My favorite size for piecing is 75/11 (using Aurifil 50wt thread). Gives me an accurate seam.
Microtex are my favorite needle type for accuracy, but recently I switched to topstitch needles because the bigger eye is easier for me to thread. If my eyes were better, I would stick with microtex.
Here's an older thread on this topic:
Needle sizes to use for piecing and quilting