The views below are taken from my personal experience and no doubt people will have other views, but here goes.
Motor used was EA Monster 27T.
I've had the LRP Q1 and Q2 (stock profile). Found the Q1 to have better punch over the Q2, so that but the Q2 out. The Q1 after a couple of months it went soft, it took me a couple of meetings to find out what was making the car slow. Did the usual things change motor, brushes gearing, brought new batteries,tried a different charger etc......Got a replacement speedo and everything was good, except a month or 2 it went soft again
Novak GTX, tried all different profiles, just always felt soft!!!
K0 VSF-1, dam this speedo can get you lost
It is a good speedo if you know how to program it correctly(Ok maybe i did not!!) but I found to get the advantage over the other speedo's on the market you had to program it right on the edge of the motor. So everytime you took a skim on the motor you had to adjust the profile. If you adjusted the profile too much then you would be back the LRP'S.
Cos you are programming the speedo like this then reliability issue's came into the equation and would cook the motor!!!This happened to me at 2 major meetings
MRT MX Pro, This Speedo is easy to setup
and is amazing, it has more punch and topend than the other speedo's mentioned (forgot to say all speedo tested same day same track) been running the same speedo for a year now and have never felt it has gone soft, never felt that the reason for going slow sometimes is due to the speedo, unlike the other ones, where that doubt would be in the back of you mind. 100% waterproof, yes we get a little rain in the UK
100% reliable and have never looked back,this baby is a 'plug and play'
What a Top Speedo