Scripts, scripts and erm... yeah, scripts. No other platform gets close in terms of script coverage, and even the AI scripts here work better and are far less complicated to get working than POVR. The community here is definitely better, too.
Beyond that, content-wise, I think the offering here maybe slightly edges out the competition, but it's not night and day. I do also sub to POVR currently, and there's a lot of same content between the two platforms since many studios are on both. I like some of the SLR Originals a great deal, but I can take or leave some of the others.
Improvements? Trouble is, all my suggestions would be based on what I want. I'm not foolish enough to think that I'll get everything I want, all of the time. My individual money as a subscriber just isn't worth that much. And a lot of what I want will be the opposite of what someone else wants.
But uncontroversially, I want the quality and frequency of the output to be the same or better. I want SLR to continue getting hard-to-get performers (and maybe try slightly harder in some cases, hint hint).