RE: Himax 2015 4100 or 5400?
The 5400 is really good with a 2S pack! On a 6.6 gear, with a 2S pack you can use the 12x6 easily, but you don't have a lot of thrust. On a 3S pack, the best you are going to be able to swing is a 10x4.7. On a 3S and a 10x4.7 you are going to be pulling about 14 amps! this is just about the limit for the 2015.
I am going to say that if you are wanting to use 3S go with the 4100! It will handle the 3S a lot better! BUT if you are even thinking of using a 2S pack go with the 5400, and just use different props for 2S and 3S use!!
I love my 5400, but I fly it mostly with 2S and 12x6. When I do use the 3S, I just prop it down to the 10x4.7.
All this being said, I have a scratch built 3DFoamy.com Cap that has 40 inches of wing. I am currently using my 5400 on it with a 10x4.7 and a 3S Kokam 1500. It flies beautifly!!!! I can generally hover at around 1/2 throttle. This being said, I am building another Cap for use with my HIMAX 2025-4200 on a MPI Metal 6.6 gear w/heatsink and will be swinging an 11x4.7 or 12x3.8! I am TRUELY looking forward to its flying!!!!!
Good Luck,
Reg