I only looked at this briefly last year around the time we go WxWorx, so will stand corrected.
The main advantage with Wxworx (mobile threatnet) is coverage (ie satellite) - (also, there have been some update to the software this year I believe?). The actual output that you can get is, however, pretty basic. Also, the hail algorithms and 'shear markers' are probably not all that great (ie your 'twisting storms' haha) as you might have found out. That said it is excellent in that it allows you to see what is going on to look at base reflectivity and identify hook echos etc and not worry to much about loosing your signal anywhere.
GRLevelX (Level 2 and Level 3, see below) relies on you being confident that you will be able to get online wherever you happen to be. This is becoming less of a problem (both coverage and costs) on the plains with each passing year. I might be wrong but I really dont see a massive advantage of full Level 2 as opposed to what you get with the Baron.
On the other hand, with GRLevel3 you will be getting the full suite of data including some excellent forecasting tools. Anyone interested in understanding the differences between Nexrad level II data (eg as captured by GRLevel2) and level 3 (GRLevel3) go to:
http://lwf.ncdc.noaa.gov/oa/radar/radarproducts.htmlIm pretty sure quite a few US chasers use GRLevelX so ST should have some user experiences.