i ran my show using xlights in 2012 and the fpp in 2013. both were reliable, both had zero lag.
i did not have my laptop tied up for two months by using the fpp.
advantages of xlights a show player
1) It works. originally written in 2010 it has been well tested
2) No addition hardware to purchase. No USB or SD cards.
3) Don't need to learn to use the web page for the fpp. You do need to learn how to setup playlists and schedule them on xlights
4) Scripts are written in BASIC
Advantages of the fpp
1) it is small, fast, reliable
2) You can play videos with your show besides lights
3) You have pixel overlay feature. While talking to people on the street you can type text and it will overlay on top of current running show. Walk to someone watching show: "Hi, what's you daughters name?" "Jenny" enter "Merry Christmas Jenny" on my phone, a few seconds later it appears on top of the current effects.
4) Can start/stop my show using iphone running a web link to the fpp web page.
5) You can have up to 64 fpp's, each with a hdmi video port, each can drive 64K channels.
This means you could have 64 hdmi projectors and 4 million channels of lights, all synced.
6) Capt Murdoch, Mykroft, Dave Pitts, Materdaddy are constantly improving it
7) Scripts are written in linux shells, perl code
so, for the extra effort the return for me is fpp will be my show player for all my future shows.
both work good, just pick how much capability u need for your show player.