Regardless of differences, like UM3X/UMPro30....they must sound damn near identical. This is not a big deal. So you can buy UMPro 50 for $200 less than ES5 but it's not custom fit but you have re-sale value.
If you do NOT have fit issues with universals, always go with universals. One exception would be my dual driver JH5's. Terrific for the price and have equal sound quality as most triple and quad drivers.
For anyone wondering.....JH5 is a UM3X with less instrument separation but brighter and rawer (less refined) presentation. JH5 rocks as intro to customs that wont break the budget. Crushes every other dual driver I have heard.
Sorry if I'm drifting away, but can the JH5 compete against other triple drivers such as the 1964 V3 or Alclair Reference?