I prefer a FBCT over color flow.
It really depends though on the look you are going for. Both fbct and color flow will hold up fine. The fbct can be cut along with the cake and I think are easier to do details. The color flow will dry hard and you can stand them up. If you are going to do color flow you better get started as you should let them dry several days.
Even more than both of those I like chocolate transfers. They are like a FBCT except you use candy melts instead of icing. They dry hard and in just a fraction of the time that a color flow takes. Plus they taste good.
I like them both, but color flow requires a bit more time. For color flow, I think you can get better detail and it it looks smooth, but it takes a couple of days for it to dry properly depending on the size, so it does take a couple of days of planning. With FBCT, it only takes as long as is needed to freeze it--again depending on the size and how good of a freezer you have. 
And with FBCT, you can place it on the cake and it is fine and perople will eat it. I think color flow tastes yucky and always take it off. I guess I do prefer FBCT... 
I started off doing color flow, then did FBCT's, now I just prefer doing edible image plaques--much simpler!
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