I have owned 2 V-Specs, own a TM928 and own a RB Modded P5x. As mentioned, the 928 is out, being a .28. Between the V-Spec and the modded P5X, I still own and race the P5X in an MBX5R, I don't have anything against the V-Spec.
This weekend I was racing and 2 friends have 8ights, one with a V-Spec and the 2050 pipe and one with the Sirio World engine. My modded P5X would out pull them both on low and high end. Keep in mind the overall gearing on a Losi 8ight is actually lower than an MBX5R, so pulling them on low end is really something. The P5X has approx. 4 gallons of fuel through it.
Hope this helps.