The Xantrex XC 2000 actually has a larger footprint than the Magnum MS 2000. The width is 12 in for the Xantrex and 12.7 in for the Magnum, The length for the Xantrex is 15.4 in while the Magnum is 13,27 (These measurements include the mounting flange, I only bring it up because some sellers list the dimensions without the flange for the Xantrex). Height wise the Xantrex is a clear winner 4.9 in to the Magnum 7.0 in. Weight isn't even close, 16.3 lbs. for Xantrex while 42 lbs. for the Magnum.
For replacing the the Tripplite the width is usually the critical dimension, which would make the Xantrex a bit easier to fit. The Tripplite is a narrow unit, which makes it hard to replace, I expect some tings would have to be moved around no matter what unit you picked.
Both units are pure sine wave inverters, with comparable efficiency ratings. The Xantrex will have a higher surge rating, but at a much shorter duration.
Cost is a clear win for the Xantrex. While you don't need to purchase a remote for the Xantrex, I would recommend the Bluetooth remote, programing is much easier with the phone app. It is annoying that you have to pair the remote to the phone every time, kind of a pain. You could theoretically run the Magnum with out a remote, it would be more trouble than it is worth. It can be a little cumbersome to program. If you were to add the Magnum battery monitor "BMK" it uses the same remote, if instrument clutter is an issue.
The technologies on these are different, the Xantrex is a newer high frequency design, while the Magnum MS 2000 is a traditional low frequency iron core transformers. This is why the Magnum is so much heavier and handles surge loads better. The high frequency units run hotter and thus will be a little noisier (fans) under loads and heavy charging than will low frequency units.
I put a magnum 2000 in my old rig, and had no complaints. I am currently installing a Xantrex Freedome SC 3000 in my new rig. I would expect that the Magnum would last longer than a Xantrex just based on the component count, tolerance and operating temperature. I can't say that it will be a huge difference, or one that you would notice in the life of the van. And then the cost would certainly offset anyway.
makes a unit that is narrow in width 8.74 in. that may be a better fit. I don't really have any experience with them, nor have I done a deep dive on their specs.