I sometimes race crits on my old 7 speed bike because I don't want to crash my new 11 speed bike. It doesn't make me any slower. I do use a 12-19 freehub on the seven speed bike so I have small jumps from gear to gear. I just have more easier gears on the 11 speed for when I am riding up hills or at a slower pace. All more gears does is allow for a wider gear range while maintaining small jumps from one gear to the next.

At the level you are riding you aren't going to notice any difference between 8 and 10 speed.

Also at 5,11 202 you are well into the overweight area of the bmi chart. The best investment you could make is working on your diet to loose some weight.