Our opinion FWIW is this:
If you're perfectly happy using your XC4 store, then don't change anything! It's still going to be very well supported by lots of good, Non X-Cart companies as well as X-Cart themselves. Quite simple really.
If you feel the need for change
and you do want to change from XC4 to XC5 then do it (as we did a long time ago as an early XC5 adopter). However.... we'd say don't bother trying to migrate either via the official X-Cart method or your own scripts or tricks etc especially if you have a heavily modified XC4 store. Create a new XC5 store from scratch (see below)
post, in another thread on the XC4 / XC5 subject, is possibly a good explanation as to why and we agree wholeheartedly with the "start from scratch"
comment that's made in that post. You'll need time and resources to do this though, don't forget.
Meaning, build your XC5 store (and a mimic dev store we'd say) on a separate server / host whilst you continue to trade with your XC4 store. This gives you time to test / check and then re-test and re-check everything
but with no loss of online trading at all. Once you've checked the checker
and your XC5 store is 100% good to go, make your DNS changes and switch over from XC4 to XC5. Afterwards, archive everything
in detail from your XC4 store for future reference and then extract all records that you might need, in a format that you can easy access locally. That's worked quite well for us.
The last paragraph is what we did (and at a time suitable for annual accounts too) We had an FAQ section explaining the changes and why XC4 accounts / profiles etc were no longer valid and advising customers who wanted an XC5 account / profile to create a new one etc (although quite often, customers order anonymously anyway and then they repeat order anonymously
which is easy to do in XC5, so it wasn't a big issue at all in the end. Your experience might vary obviously but...
Finally, if you're totally new to X-Cart, than it makes common and commercial sense to opt for XC5 because a) you cannot buy an XC4 licence now anyway
but seriously b) Once your'e past the steep learning curve and feeling comfortable with creating your XC5 own modules (or buying very well developed third party XC5 modules, of which, there are quite a few) then XC5 can be very heavily customised to your satisfaction, but in a way that dispenses with "patches" and "reworking core coding" etc when it comes to installing the latest XC5 upgrades.
XC5 is far from perfect, but it's 1000% better than it was, when it was first launched. We're really quite happy with it (most of the time) these days.