From what i’ve read I don’t see any reason upgrading 10.2.300 to 10.2.500 (or 600) would be an issue. Is it best practice to step these up one at a time?
Documentation says you can jump from 10.x to 10.2.600 as long as you follow the procedures from what i can tell.
Epicor Release Upgrade Guide
Epicor ERP 10.x to 10.2.600.x
https://epicweb.epicor.com/doc/Docs/Epicor10_ReleaseUpgradeGuide_10xto102600x.pdf
Upgrades are really good these days. Epicor 9 was a whole other story. We are going from 10.2.400.6 to 10.2.600.7 next month.
I have converted databases many times with no issues. 10.2.500.x had a couple of small ones, but those were resolved in the current releases of 10.2.500.x
Lots of performance increases for MRP and others in 10.2.600.x
I would always recommend upgraded to the latest release (currently 10.2.600) when upgrading. If nothing else remember Epicor supports a 2 year active updates window for a release. After that if you find a problem you will be told to upgrade rather than being able to ask for a fix in an update. Based on that the later version you update to, the longer window of update support you open up for your company.