This may fail, I am not good at photo posting. Below you should be able to see some photos comparing the 550xl and the TLR7 and TLR1. I like the switching on the 550xl even though it is arguably too easy to activate. The paddles sit higher than a TLR1 and have less movement required to activate. They only activate with a downward push. if you tap it will be continuous if you hold it will go into momentary. If the picture are visible you should be able to see that there is a angle in the front of the TLR7 that is not matched in the 550xl. This is what is stopping the 550xl from seating in the holster as shown. I am hopeful that the 550xl will work with the Tenicor holster as this portion is not molded for a specific light. I will likely have an answer for that on Monday evening.
As far as light output i would say it is comparable to the TLR7 in overall "brightness" to the naked eye. If you shine my two examples on the wall the 550xl will over power the TLR7 but my TLR7 didnt have brand new batteries in it either. the hot spot appears to me to be very similar sized and the color appears whiter with the 550xl.
Just to be clear I am not high speed or low drag. I do not face shoot outside of occasional good fortune on X-box and I'm not even cool enough to have a blog. these are all just first impressions after opening the box.