No matter what, you're going to have to pay for a better trigger. The only question is, buy it yourself or pay Remington to upgrade it. That's basically what you'd be doing buying the XCR.
There was a nearly identical thread comparing these 3 rifles here on THR within the last month or two at most. I posted in it. Good info there.
As far as accuracy goes, they're all equal (referring to barrel/action). Trigger? The SPS and LTR are equal, the XCR has a better trigger - but I doubt it is better than buying an aftermarket. Like Dryhumor, I have the Riflebasix varmint trigger and it is excellent.
Stock, the SPS has a Hogue, the LTR an HS Precision, the XCR either an HS or a B&C I can't remember. Basically, the LTR and the XCR have "real" stocks. Rigid stocks that free-float without issues and that have aluminum full length bedding blocks. This improves accuracy. So the LTR and XCR will beat out the SPS simply because of their superior stocks.
Finish - the LTR and XCR have a quality finish. The SPS has an inferior finish. It won't rust, but it isn't as durable nor as forgiving of lesser care. You definitely want to keep the SPS oiled.
I own the SPS. I upgraded the stock to the HS Precision (used) from a PSS and bought the Riflebasix trigger. Came in cheaper than the LTR, which is cheaper than the XCR. Have just as good of a stock, and a better trigger. Barrel and action are all the same. Only thing I do not have is a higher quality finish.
Rifle shoots 1/2moa.
SPS is the best choice for a budget. You'll save at least $100 that can go to a quality base and rings. However, you have to do some more buying and swapping. LTR is somewhat middle of the road. You get a good stock, and a good finish - but the trigger is not the greatest. The XCR is pretty much a one-stop-shop. You get a good finish, good stock and an adjustable trigger that should be good enough. Of course, it costs the most. But you avoid having to buy after market parts and doing anything extra.
I like to tinker, so the SPS didn't bother me one bit, I got the same results for a little less money. People who want the total package without any fuss should just pay the higher price for the XCR.