The AA battery aspect of the Retras is a concern for sure , which is also one of the reason for increase in size and weight. There would be bit of expenses included in the purchase of numerous batteries and the charger as well.
Retra strobes up to and including 4th gen (Pure, Prime+, Pro Max) are powered by AA cells. 5th gen (Maxi) use 21700 type Li-Ion batteries, which are individually larger, but you only need two of them instead of eight AAs.
Also after Inon's most sought after Z330 being discontinued, i suppose there is nothing much left in compact strobe bracket except for Retras. But they come with a $$$$ tag. And if one wants to keep it low then it has to be compromised with the size, BS, Marelux etc.
Retras, regardless of model, are somewhat larger than Z-330s. It's not a huge difference, but it's noticeable. Sea & Sea YS-D3 series is also somewhat more compact than Retras. Another option, if you want to cheap out, is SeaFrogs SF-01 - the feature set is quite basic (no TTL or HSS), but it's got good power, uses two 18650 Li-Ion cells, size and weight is similar to YS-D2/D3, and you can get a pair for well under $800.
Retra Maxis, if you have the budget for them, are a good choice - I've been using a pair of Retra Pros since they came out, and I'm quite happy with them. That said, I'm curious to see a real-world comparison between the straight bulb in them, and the circular bulb in previous gen models.