I have both...both are real good. V-Spec is a little better, about 45 seconds longer run time and more bottom.
The Ninja is very solid also, I have a bunch pipes, the best one I tried was the cheap Ofna 053. I have the 2053 Ninja twist-lock ($135
) and the 053 is better. Oh yeah, switch from a #7 to a #6 plug.
If you really want a bad-ass motor. Get the Ninja, send it to RB Mods and run a 086 pipe. Just as fast as a Speed and 10-11 minute run time. My buddy runs this and every time I pit for him, all I hear is "Jesus Christ, what motor is that Tristan guy running?".