I have both in 8,9 & 10wts. tough question, but, IMHO, here goes. The RPLXi has a bit softer tip than the Xi2. The Xi2 is a rod that seems to have more feeling during loading. They both have a lot of butt strenth for lifting. If you do a lot of travel the four-piece Xi2 can be stowed in its case in luggage. The RPLXi is generally 3-piece, not conducive to sticking in luggage, unless you can get your hands on the 5-piece.
Both great rods. If price is a factor, you can generally pickup a used, but not abused, RPLXi for about half the cost of the Xi2.