question on draw evaluation

[Houdini]

Some draw endgames require not only the pure material is under centain conditions, but also require the position of some pieces are eligible if they are not the strong side.
To analyse the position condition in the evaluation function, or just let search to do it, which choice is better?

Engines that rely on search only will make the wrong decision when trading into certain endgames that appear to be winning, but are in fact drawn. Below some examples of basic endgames that a strong human player will recognize as draw, but most engines not:
[d]6k1/8/6PP/7K/8/2b5/8/5B2 w - - 0 1
[d]8/2K5/3P4/2k2b2/8/8/4B3/8 w - - 0 1
[d]4R3/1K6/8/2k1p3/8/8/8/8 b - - 0 1
[d]7Q/8/8/4K3/8/8/2pk4/8 w - - 0 1
Without tablebases or special evaluation code an engine will require a very deep search to establish a draw score.

[bob]

Same thing. Search will eventually end up at a 3-fold repetition or 50-move draw. That's the point of encoding these rules. Of course this is better done in the evaluation, and for this case (bishop + wrong rook pawn) many programs do evaluate it as an outright draw via special code in the eval. Crafty has done this for years. Even versions of Cray Blitz had code to recognize this kind of drawn position (we had to avoid trading into a +4 position (ahead bishop + pawn) that was a dead draw. But for any of these cases, search will eventually recognize the draw, because that is what search does when it can reach sufficient depth.

Well, that's obvious. Search will do everything if you give it enough time...
I was referring to your sentence "Opposite colored bishops are not automatic draws", however, because it sounded like you hadn't understood what he meant by "wrong bishop".

I took it in the more liberal sense. Which would include both B + wrong rook pawn or B vs opponent's opposite-colored B.