Excel
I fly both an Excel and an Ultra and have experience in the Encore.
The cockpit in the Excel is hands down better roomwise and has less glass area, which means less heat in the cockpit. The Excel cabin height is a huge plus over the 500 series fuselage height of the Encore. The Excel baggage area is huge compared to the Encore. You can load 8 golf bags straight up plus eight medium sized bags. Try that in the Encore. Also, a nice larger lavatory.
The APU is a big plus, especially on a winter night at a remote airport having no GPU. No dark airplane before the passengers arrive.
If you are looking for value in used market, there are many Excels for sale in the $4.5 to 5.0 MM range. After 3,000 hours in the 500 series Ultra/Encore/Bravo aircraft, I am sold on the Excel.
Good luck,
CC