The SL's have a
1. shorter cabin with a bench seat to port. The XL has twin capt chairs and side facing seats behind them.
2. I believe there is also a bulkhead between the berth and wheelhouse on the XL and just a curtain on the SL.
3. I also believe the 25 SL was a notched transom boat and a full transom and bracketed outboard on the XL.
I am told the newer parker 25's in the XL and SL are both 16 degree deadrise boats vs the 14 degree deadrise hulls on the previous mod v's.