Why are UCI engines in general stronger than Winboard engines?

Strongest UCI engines - Stockfish, Komodo etc. [Average rating - 3388]

Strongest Winboard engines - Crafty, Fruit etc. [Average rating - 2896]

go to school to find out

I don't really know, but I'd guess that the UCI interface is just easier to program. Bob Hyatt, the Crafty programmer, claims that UCI engines turn over a number of decisions to the GUI, and he clearly doesn't want that for his engine. In terms of ratings, I doubt that it matters much which engine protocol is used.

 Yeah, I completely agree with EscherehscE, it is not a mater of UCI or Winboard, it is just a matter of who made it and how it was made, there are a lot of UCI engines weaker than Winboard engines.

This question sounds too easy, maybe we are getting trolled?

I was giving him the benefit of the doubt.

We got trolled!

Here's what I read from the link below.

• Because of the "stateless design" in UCI, it is difficult to do book learning.
• UCI is too constraining and restricting for authors who want to add new features.

http://horizonchess.com/FAQ/Winboard/uciwinboard.html

I'm familiar with the Horizon web site, but I didn't know about the Winboard vs. UCI debate posting. I'll give it a read; Maybe I'll learn something interesting.

And there are more contributors to UCI, making it better.

I think most developers are using UCI today.  There are still some who prefer Winboard, and it does have some advantages that UCI lacks, but UCI is probably better and it's certainly easier.  So UCI has stronger engines primarily because it's the preferred protocol of most developers today.

There is nothing in either protocol that will strengthen or weaken the engine, however.