Despite the couple of differences you can see from the spec there are actually quite a few between the two.
I have a Pitpro 140XR and ride with a MSO Pro
There are just so many things that I have upgraded on the Pitpro already that I would not have had to with the MSO. I ride motard so suspension, brakes, engine, blah blah blah all matter to me.
Its all the small things that really make the MSO the better bike, pitpro has barely usable front brake, mso whack a bigger rotor on to suit the caliper location and they are wicked. Simple stuff like say the throttle even, pitpro one has to be modified because it is a **** design and constantly has slack or pulls on the cable and revs your motor, MSO one has no issues. The exhaust header (might be different on 150XR) on my 140XR is poo, like real crappy bends, MSO is a very nice header with great bends.
Pretty much to the point that if I could get back what I have spent on the Pitpro I would go buy a MSO 140SR (I like the KLX ones because I'm big...) and probably wouldn't change it at all. Put my wheels on it and ride the thing.