TBH the word "best" is so relative it's meaningless.

Effects color your tone, that's what they do--of course the bypass is something that needs to be uncolored.
Here's what we need in order to help you:
--What is your actual budget? (Please don't say "won't break the bank"; state an actual number.)
--What effects are important to you? Some multi's are better at (for example) modulation and reverbs, while others are better at amp modeling, and yet others are designed to emulate a guitarist's whole pedalboard. Almost none of them are good at overdrive or distortion, but some are "less bad" than others at that.
--Will you be combining it with other effects, and if so, which ones?
Also you'll want to read through the FAQ stickied in this forum.