DSLR, Compact or Video?
How big are the lights, and how much do you want to spend?
'Best' is a very relative term, we need to know 'what' they are going to be the best for.
As you have asked about trays, I assume you mean a tray for a compact camera, allowing you to attach strobe arms.
ULCS make some nice kit.
Ikelite isn't bad (I have Ikelite, because it came with the strobe (which is also Ikelite))
TLC by Aquatica
10 Bar make some nice 'flexi' arms (there are also some copies on EBay)
I made my own when I had a compact camera (LOCLINE)
On the dive we did on Saturday, most people looked to have ULCS (certainly going by the shape of the clamps), but these were generally on DSLRs, so the arms were mounted direct to the housing/handles.
It's important to remember that strobe/s and an arm system are able to migrate with you when you go to a new camera/housing combination.
"The best" is probably the ULC system here or rather some variation of it. I say that because the linkages are secured by O Rings, which makes them about as steady as it gets. There's nothing as bad as getting that brilliant shot only to find that your carefully positioned strobe has inexplicably moved. If, for some reason, the ULCS system moves, it also shudders which you'll be able to feel. If you can't feel it, chances are that you've not tightened the ball joints enough.
The TLC system nowadays made by Aquatica is good but not as good as ULC for the aforementioned reasons. One other detrimental thing about TLC: the tightening knobs are round, which makes them a bit of a PITA to tighten properly. I have had both, I still have the ULC one and I doubt that I'll change it anytime soon. It's fairly long in the tooth now and has gone through various iterations of cameras/strobes but it still works superbly well. The only things I've replaced are, periodically, the O Rings but, yes, I've also painlessly added to the system. BTW, these O Rings are not to be greased (I've seen it happen ).
Incidentally, it seems to be accepted wisdom amongst some that if you buy a certain strobe you need to buy that manufacturer's arms as well. That's complete and utter nonsense, the (modern) strobe hasn't been made which can't be easily accommodated on a ULCS/TLC arm. Some strobe manufacturers' arms systems leave something to be desired, understandable really, they prefer to concentrate on strobes, arms are often an afterthought, provided simply because some people ask for them because they're too lazy, or ignorant perhaps, to find out what works for themselves.