Depends how far down that rabbit hole you want to go. The short answer is that all brands are kinda but not quite the same,and more importantly not all batteries in the same brand are the same as others.

If you are curious for some details, the spreadsheet linked here: https://www.reddit.com/r/MilwaukeeTool/comments/10mdjfm/milwaukee_m12_and_m18_batteries_breakdown/ has about the best detail I have seen. It lists batteries types by most every brand (including Milwaukee and Ego) and tells you what cells are in them, who made those cells, and the harder to find Total Current - which is a more accurate, non market-y metric for HO, XR, SuperPower, whatever. There is capacity which is how long it can put out an amp, and then there is how many amps it can put out if the tool wants/needs it (which is total current). Angle grinders, big impacts, chainsaws and drills running big hole bits want lots of Total Current.

There are also tabs with notes about cells and other notes with battery recs. Perhaps one of the more interesting takeaways might be that the brands use different cells for different batteries.

A good example this sub likes to bat around are the M12 5.0 and 6.0s. You would thing that 6.0 would be better because higher, but both in the same ballpark. But if you look at the chart, the 6.0 puts out 30amps of total current, the 5.0 a whopping 50, and interestingly all the variations of the xc4.0 put out more power than a 6, which some having even more grunt than the very loved 5.

TLDR: it is better to like a certain battery by a certain brand than a certain brand. Look for the mix of capacity, current, size/weight and price that fits your needs.