Nick, I beg to differ with you.
The only differences between an SW4024 and and SW4024-MC2 are (1) Listing labels and (2) the software, contained on a ROM. Otherwise, they are physically identical. See my extensive write-up on this here:http://ourodyssey.us/bus-e-trace.html
To answer the rest of the original question:
Xantrex has purchased several formerly independent inverter and charger manufacturers over the years, resulting in a bewildering and often confusing array of products and model numbers, often with substantial overlap. Among the former brands now part of Xantrex:
Xantrex has been inconsistent about marketing these products both with and without the former brand name included. So sometimes you will see only "Xantrex SW4024," sometimes "Xantrex Trace SW4024," and sometimes just "Trace SW4024." These are all the same product.
Note that there have been other products over the years from these labels with a designator of "4024."
Anything you are looking at today will be one of two products:
Xantrex Trace SW4024 (either base model or -MC2 variant, as discussed above)
Xantrex Sine Wave Plus 4024, often referred to as SW+ or SW4024+
These are very different products.
The SW4024 (and its siblings, the SW2512, SW4048, and SW5548) was considered by many to be the gold standard of inverter-chargers for a long time, although more modern products from competitive vendors such as Outback have eclipsed that title. Unfortunately, this product is now discontinued, with the exception of the RV/Marine version the SW4024-MC2. That being said, there is still a lot of unsold stock in distributor inventories, so one can often find this model in stores or on eBay as "new."
The SW+ series effectively replaces the older SW series. It is newer technology, so one of the advantages will be more user-friendly menus (one of the serious deficiencies of the old series). Also, efficiency has been improved very slightly. However, the down side is that they have quite literally removed some of the features that made the SW series so good. Automatic Generator Starting, for example, which was built-in to the SW series, requires an optional, extra-cost module on the new SW+ series. And, of course, the price has gone up.
The SW4024-MC2 (and sibling SW2512-MC2) is still being made. I have a suspicion that the only reason for this is the cost of UL listing and USCG approvals that would/will be required for the SW+ series to move into the marine market. Also, technically, they now need separate UL listing for the RV market. So the SW production line is still operating, although you can't get a non-MC model from Xantrex any longer, even, if reports I'm hearing are true, as a replacement for an existing unit that has crapped out.
Technically, the newer SW+ product is not rated for mobile use, and so you risk having any warranty claims rejected by using one in your coach. Also, unlike the older series, there is no data to suggest that the unit has even been tested to the UL standards for RV and Marine products, thus adding another element of risk.
If you want a Xantrex product, I suggest you stick with the SW4024 or SW4024-MC2. That being said, you might want to have a look at the Outback products as well.