I would have to say that The Caesar's group (Total Rewards) is the easiest to get comped rooms on the strip, albeit for lower play you will be limited to the lower end properties. We were staying at a Mlife hotel and checking out other casinos. tried Caesar's palace and signed up for total reward cards there. We played minimal in that casino, maybe $500-750 coin thru by both of us (not each). Checked the TR website online a few weeks later, and low and behold we were able to get 5 comped nights at Paris a few months later. Tip, use the calendar function. This is for comp rooms only, they do not seem to give out much for freeplay, resort credit, or food for us lower rollers............but I am more than happy with a free room, can always find somewhere to eat! Also, if you are a couple, if each of you sign up for a card it will make a difference on your room comps if both #s are used on the calendar page. Good luck in your search!
For your first trip? Not any great choice. Tease offer for a return trip? CET. Since you have been to Vegas 25 times, I would guess you have some relationships already?
+1 for CET/TR. Specifically, The Linq is a personal favorite of mine. I always have comps for them and I would consider myself a relatively low roller ($15-$25/hand blackjack, usually). As for Mlife, a minor annoyance is that the offers I do get from them usually seem to be of the "Call Mlife VIP services and mention (some offer code) to book" variety. No. I don't want to do that. Just give me an offer code that I can put in while booking online and I'll be more than happy to consider it. That being said, I don't usually do a ton of gambling at Mlife properties either, so that may have something to do with it.
Definitely CET total rewards. Husband and I are low rollers usually bringing ONLY about $600 a day for us to share (7 day trip usually) we are both platinum and can get 5 nights comped at just about any CET property. weekends too. We usually go to Ballys or Paris just cause we like that location.