if you have the same card able to convert:
a) 1$ of power cost per day into 2$ crypto value in x11
or
b) 2$ of power cost per day into 4$ crypto value in n-scrypt
The long term winner should be option b)...
...and there is X11 fpga (and ASIC then) real risk also...
...and Nvidia 750Ti solves power usage and heat problem completely
(while AMD is nowadays just A Mining Dinosaur

)
This depends on whether you're mining to hold or mining to dump. If you're betting on the future of a coin by holding, you're essentially buying it with the cost of electricity used to mine it (rather than paying the higher market value of an exchange). No, it may not give you as much BTC if you mine a higher profit coin and immediately dump it onto an exchange, but that's not really a good thing for the health of a coin if it just exists to con investors out of their BTC (regardless of whether you're holding the BTC or investing your profit in a different coin).
X11 FPGAs are a rumor. There are a lot of GPU miners who have been pushed away from LTC (ASICs) and DOGE (reward halving) - they've gone to X11/X13, not Scrypt-N as VTC's developers predicted. The big migration to Scrypt-N may never happen.
On the subject of GPU brands, if you've already invested in a rig, you use what you have. There's really no good reason for anyone to be buying up GPUs today - profitability, even in "ASIC resistant" coins, is presently terrible. Overall investor enthusiasm in altcoins in general is down. Probably due to the multitude of crap coins being released every day.