It's unlikely that OP would be getting Alienbee - PCB can't be bothered supporting anywhere outside USA (plus there's that weird US voltage business - most of the rest of the world uses 230v). Much depends on ready availability in a prospective purchaser's home country - eg even without the voltage business, by the time Alienbee is imported into Ireland and the 23% VAT is added on (plus the shipping charges too) then they become more expensive than more readily available stuff developed specifically for 230v markets.
Yes, the Bowens mount is the most widely available. But it too is not without it's problems. Firstly, the narrowness of the throat restricts multi-flash applications quite markedly. The other thing stems from the copying/cloning business. If, big BIG 'if', each of the companies who have copied the Bowens mount had actually copied a genuine Bowens mount then much would be OK (setting aside the morality of cloning). Unfortunately, it seems that many have copied other people's copies, inaccuracies have been compounded and they don't all fit! So there are quite a lot of Bowens S-fit look-alikes about to confuse matters.
Just this minute checked with a friend in Dublin who uses Elinchrom - the Eli 'throat' is about 23mm greater diameter than Bowens. So there's more scope for using a couple of speedlights in one modifier if desired. Set against that is the greatly reduced availability of Eli-fit compared with Bowens.
IMO, this side of the Pond I think your choice is simply between those two types. Anything else is going to create more problems than it solves.
I have 3 Photoflex speedrings and 2 of them wouldn't fit my Bowens flash units without surgery. The third one is a beautiful fit.
Last week I received a Lencarta standard bowl reflector/modifier and a Godox standard bowl reflector/modifier (same maker, just different labels). Neither of them will fit my Bowens units at all (too big diameter) though they are lovely and snug on Chinese-made flashes. Conversely, I have a genuine Bowens grid reflector which won't fit the Chinese flash units - the lugs are too fat. They are all described as "Bowens S-fit" and yet for universal application they all require gentle (?) adjustment with a file and a big 'ammer. Absolutely bl**dy infuriating - even for someone well equipped with aforementioned "adjustment devices"
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Best idea is to see what O'Leary Cameraworld have in stock (or the very helpful Bermingham's
on Burgh Quay [very near O'Connell Bridge] next time you're in Dublin) and take it from there. There's nothing quite beats laying your hands on the gear!