I thought my MC-E light bezel was tight enough above water but as soon as I went down to 60+ fsw, it was very loose -- about a couple of turns. Luckily it didn't flood.
At first I was also contemplating buying another light but then decided to dive right in and bought one because it had a higher lumen and it's new. Ok, I don't have a real good excuse.. I just like LED lights.
My SST-50 light is still in transit so I hope to get it sometime this week. Bad part is my drysuit is in repairs so I won't be able to get any beam shots underwater.
From CyprusSeb's review, it looks it's marginally bigger lengthwise and bigger in diameter. The hotspot seems to be a bit bigger too but from the looks of the picture, he's only about half a foot (or less) away from the wall.
We're comparing 900lm vs 1200lm and I have to agree that I don't think it's going to be substantially brighter -- at least in human eyes. But if it will give me a bigger hotspot with a less doughnut, then it'll be a plus in my book. I'm also concerned about the duration of the SST-50. The SST-50 isn't as efficient as the MC-E. Then again, I'd ok with it if it can last a couple of night dives.
Let me know if you dive up here in BC. I can show you the lights first hand.