The Joie XL doesn't offer you any extra benefit as it only adds a high back booster mode and it's a heavy, awkward booster anyway.
IMO having worked in a baby store, Cybex's design of the features like the inserts and straps are a lot nicer to use than Joie. It feels more premium. You need the "Plus" fabrics to get one which is cotton/denim like though so less sweaty - and bear in mind, all car seats are sweaty to an extent.
Build quality wise both have excellent safety results, Cybex tended to get returned more because the sliding shape of the base means dirt from the toddler's shoes gets trapped in the mechanism and then the seat stops spinning. But this doesn't happen for every user. Joie tend not to have issues like this, but one of the ways they reduce costs is to increase the gaps between the different isofix fittings, which means that you can get a slightly less snug fit with the Joie seat in some cars so it will move around in use and rattle. That is not a safety problem but it can be annoying.
The reason the car seat groups are recommending Besafe Beyond is because at the moment it's the only rotating seat which lets you harness up to 125cm rather than 105cm. I think Avionaut are meant to be releasing one soon as well. I'm surprised you can't try the Besafe one in person - I thought John Lewis stocked it? However, it's an expensive set so you might not be keen on that outlay anyway.
At 16m it's possible she will go down a centile band or two but basically, is it more important that this seat rotates or lasts you to the high back booster stage? Do you think you'll be likely to have another child in the next couple of years? If so it doesn't matter so much if it doesn't last her for the full stage, as you can hand it down and get something which bridges the gap and can be handed on again in turn.