Both 2.1 and 2.o pro are good and basically the same. The major different is the firmware pre-loaded, case, and accessories which come with. For me I will go version 2.1. It has bigger cooling fan, whole upper case made of aluminum, and pre-load with stock mode firmware. Buy a program card you can easily switch the fore and back btw modify and stock.
I am using sp 2.1 prostock with (100528mod) software with 4.5 turn SP V2 motor with gear ratio 8.9. It work fine so far with 8 minutes run in TRC, it's degree around 62 on esc and 52 on motor. I try 4 turn sp v2 motor with 9.7 gear ratio and esc overheat when I hit full throttle.
I am using 2.1 prostock in TRC with software (100528mod) with 8.9 gear ratio with 4.5T SP V2 motor. In 6 minutes run it's degree around 60 on esc and 50 on motor. The esc setting is
1:1
2:2
3:3
4:6
5:3
6:1
7:1
8:1
9:1
10:1
11:1
12:2(turbo rpm)
13:9(turbo start at 15000 full throttle)
14:3(turbo delay 0.3 seconds when full thorttle)
15:3(turbo punch -2)
When I use 4T sp v2 motor my setting on #9 is 1 (AMTS-TIMING is 0) and my gear ratio is 9.7 with software (100528mod). My friend is using hobbywing v2 120a esc with LRP x12 4T same setting have no problem at all.