I was looking at the XPS 2-0 recently, and it's definitely the best option out there for EOTechs. Most people don't need NVD compatibility, so the 2 series is a good way to save some money as opposed to the 3 series. I have heard that the transverse mounting of the battery has increased reliability.
I own 553 and use a 552 for work both work great. I dont think theres a real need for the NV button, if you plan on using it you can adjust the brightness down enough to use it with NV. The real question is what batteries do you want to use AA or 123? I love my 553 but 123V batteries can get expensive. Im not a fan of the 3x magnifier, own one and will be selling it soon, can't say I have any experience with the 557 even though I've been curious about it.
I have been running 553's on M-4's, SIG SBR's,and a Noveske10.5" Mk18 for over 5 years with no problems period.Plus all my other lights and battery needs are 123's which makes life alot easier.My oldest 553 has been abused some ,dropped, water logged and been through 3 ,12-16" snow storms, no problems. Excellent kit!