The Merc. I helped a friend break-in his SHO over the weekend. I was not impressed after following break-in instructions for 5 hours, I opened the 2018 Skeeter FX21 Limited w/ a 2017 250 SHO 66mph with a light load. Took it a long time to reach that speed. Drove a 2017 521C Ranger with tournament load 74mph and got there pretty quick.
Whatever.....my TZX190 will get to 66. I have a good friend who lets me take his FX21 out with his SHO 250. It does 72 gps all day long. It's a dual console and loaded with his crud and all the stuff I feel like loading on top of his stuff he leaves in it.
Get the SHO. Having the best, and what you WANT, is worth waiting to get. Get the ProXS and you'll be kicking yourself in the [censored] every time a SHO fires up at the ramp. So quiet, so refined. And still plenty fast.