400 points

I play 5/5 and 2/1 games. My rating in the former touches 1800. My rating in the latter seldom rises above 1400. Without playing me or knowing anything about me what would you say would lead to such a gap? What conclusions can you draw about my style of play, strengths and weaknesses?

Why this somehow shocks people ill dont know.  

If you have more time to think, you play better.

the handicap of less time applies to both players though. So If I have less time so does my opponent. Why this somehow has escaped your notice I do not know.....

Exactly, youre both making mistakes.  The player to make the second to last mistake usually wins.

an undeniable fact for games of either time-control. Your mode of thinking applies only for handicap games where I get a time control of 2/1 and my opponent of 5/5. Then You will see an easily-explained rating difference. Just like if the reverse your true you would see me "mysteriously" gain another 200 rating.

You have the same problem that I have. Your brain is not able to process the entire board quickly. I can play Class A chess at normal long time controls (I've even beaten candidate masters in OTB rated games) but I can't get to 1300 in 2+1 bullet to save my life. I think that it is similar to fast twitch vs. slow twitch muscle fiber. Some have it and some don't.

interesting.... your rankings gap is even more stark than mine. would I then be presumptuous in ascertaining that you prefer positionally intricate games with long-winded, long-term strategical nuances over tactically sharp combinations and sacrifices? or vise-versa? not sure.....

I enjoy both types of games..........but I cannot play sharp tactical games in short time controls because my brain simply cannot work through all the calculations quick enough.

"Back in the day" i could routinely qualify for the club G10 championship.  Now?...I cant even get close to qualifying.  Age takes its toll.

The time applies to both players...

Why SO MANY people make the mistake of not noticing this, I don't know.

Well first of all you're facing a different group of players, and your rating is being measured in relation to that group.

Lets imagine a club where only GMs are allowed to play, and everyone starts at 1200. The strongest GMs in the world, if they played there, would not be over 1500.

Just an extreme example to remind you it's not an absolute measure like height, or how fast you can run. It's dependent on your opponents.

Most beginners are uncomfortable with fast time controls, so it's easier to get higher rating where the beginners play (long time controls)

Most hard core and titled tournament players play their serious chess OTB, and are uncomfortable with slower time controls online (cheaters) so it's harder to get higher ratings where they play (fast time controls).

So most people have at least a small gap between ratings like this.

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But ok, maybe we also notice that most people only have a difference of 200, while you have a difference of 400. In that case I'd guess you don't have much experience with the faster time control, and if you played it more often, you'd eventually have a gap that's closer to the gap most people have.

Strengths and weaknesses? Not really. It's just how fast you can apply your knowledge, and how well you can manage your time. If you're used to thinking for 10 seconds per move you're probably going to lose at 2/1 even if you know more than your opponent, simply because you couldn't pace yourself.

Oh...

but it's true that part of pacing yourself in the very fast time controls is all about very fast recognition of basic threats, and very fast calculation of basic 1-2 move captures and threats.

This could be considered a skill in itself.

kewl.... some nice responses of all. thanks guys!

People are simply different people; some prefer (and are better at) shorter time controls, and some are better at longer controls. Additionally, there are some really strong chess players who take forever to move, so any time control other than classical is a challenge. Like anything else, to get better at a specific time control - practice it. For the most part though, a chess player rating should be within a few hundred rating points, regardless of time controls. 400 points is on the verge of uncommon, but is not too far off; around 300 or less variance I experience as more common. 

However, there are exceptions that should be noted: 

1) A lot of bullet chess often kills blitz chess, and vice-versa; this is because your brain becomes "trained" to only spend a certain amount on each move, if you constantly play at that time control. I even find this true with blitz versus daily (classical time control) chess - but this will not show up as much because of the quick pace of bullet, or blitz where as a little variance in move pace for classical means less - as you usually will not lose a game for taking an extra glance.

2)Some players simply can't play a certain time control well, almost regardless of how much practice they get. I find this true because more pre-game study/theory is required as the time controls shorten (as there is less time to think OTB if the time controls are shorter), or simply the "rush" some people can't handle as well.

3)There are obviously several other reasons why rating may vary a lot, but it is often a red flag that the profile account user may be cheating/sandbagging/directly using an engine etc. This fact alone does not prove cheating, but it is a common indicator (as is a relatively new account, "computer looking" moves, use of uncommon openings/sidelines with less theory etc.)

What can I tell about you if your account is honest? Well ... If your longer time controls are better, I can hypothesis that you know less theory, or can't calculate too quickly - which I may exploit via sharp lines with many calculations. If your fast pace rating is exceptionally higher than your longer time controls ... I can guess that you may play tactical (or unsound lines/gambits) with the intention of calculating quickly, or catching the opponent out of theory. If I was facing this type of player, I may simplify to "obvious", " dry" positions where their tactics and excellent calculation ability will not help them. Getting a positional endgame is often what these types of players hate.

Although I will note that between blitz/bullet, or ratings close in rating (regardless of time control) tells almost nothing.

Keep in mind that exceptions exist; one example being an exceptionally strong player OTB only using their account for blitz, or faster time controls. Likewise a rating like 1500 even, or 1000 even, give almost nothing - as they could be new accounts, or simply never played that time control.

There is a threshold most people cross where if they have less time they can't think of coherent moves. My threshold is right around five minutes, any less and I have trouble thinking of ANY move much less a good one. For that reason I never play bullet chess or 3 / 2 , it's just not enough time.