I'm thinking the bent ones are best, but what have you found that works best and where can I buy them?

I've been thinking about getting the long ones.

Wurth for a six.
Available through distributors or BMW shops

Buy a bent one and a straight one- they are cheap. That way you can find the one you like. I like straight ones, there have been times when the bend seems to get in the way.

You can also get "Go-NoGo" feeler gauges.

For setting valves at say .006.
You would use the gauge that has the thick part at .007 and the thin part at .005.
If the thin end "Goes" and the thick end is "NoGo", then you are at .006.

They work great for setting valves (unless your valve lash is zero).
So I bought a set, then changed to chromolly pushrods, so I dont have a use for them anymore :-)

Bent ones fit if you remove the one you need for the valve, use that, a dime, and a wrench.