TRX 2012 or 2013??
TRX 2013 is faster and has better low end.
In general, TRX is recommended for intermediate/advanced riders (comparing to the Argo) basically because it is a fast turning kite and need more input (than the Argo) to get a better low end.
Turning speed can be adjusted to get a slower turning. Turning speed can be reduced also using a shorter (smaller) bar.
Adding extensions (longer lines) will reduce turning speed and will give you better low end.
If you had some lessons I suppose you used smaller than 10m kites, possibly turning much faster than a 10m (but pulling less).
The Argo would be easy for learning, but I???m pretty sure that with the TRX won???t be much more difficult.
The Argo can be easier to re-launch, but TRX 10m is also easy. Normally, small kites are easy to relaunch. More difference could be appreciated in bigger kites
About the size, will depend on the predominant winds in your area. Try to know wich sizes are using there other riders or wich are the average winds there.
Your wind range will be reduced when you start (while you are learning), but with some practice will increase a lot. TRX has a great wind range.
Sure when I learned the kites were not the best for learning (old C kites)... and I'm still here

Always try before decide if you can (even on the sand). Don't buy it if you don't have a good feeling with it or you don't feel comfortable.