Try them both. I predict that SG will be crisper, Excel will be softer. You probably string your SG higher, but pls try RPM 18 gauge in the mains at a tension in the mid 40s, with the crosses 4 pounds higher. If you tend to hit long, go up 3 or 4 pounds, but try to stay under 52 pounds for the RPM. If you tend to hit shorter than you prefer, try lowering tension a couple of pounds, or add some weight to the handle end of the racquet. Remember, RPM is great at low tensions. Experiment--this is really magic stuff.
I think that you will find that you can hit with significantly more topspin, and open the court with wider angles.
After a few hours have accumulated on the strings, butter them with a greasy hand lotion each time before playing.
Pls report back on the performance of the strings and how long they last you, we are all learning.