I use 1/8 BB for all my portrait style projects but I think it depends on the pattern as well. If there is a lot of fretwork cuts in it the project 1/8" is the way to go. If not you may want to add some depth with the 1/4". I do my cuttings a little different than most I guess. I stack cut 3 - 1/8" BB but I also sandwich 5 pieces of card stock in between the top and middle layer and 5 pieces of card stock between the middle and bottom layer. The 10 extra pieces are pretty close to 1/8" thick. So instead of having 3 or 4 finished projects you have 13. You can sell the card stock cuttings for 1/2 the price as the wooden ones or if you are like me, give these to family, friends, or fundraisers and still keep your wooden ones to sell at a higher price. I normally use wedding invitation stock because of it's lighter color but you can get bold and use silver, black, grey or whatever color you want to experiment with. Just a thought.
Terry