I'm quite surprised that 3 xr15s at 100% are about half the PAR at the same area. I'm glad I switched to T5s a while ago. I have been itching to get a meter on my tank to see where I'm at but it's impossible to find one locally.I've tested PAR in my tank with a BTM 3000. The tank is 40 x 21 x 21 and I have a 36 inch 8 bulb Sunpower with 4 blue plus, 1 coral plus, 2 actinic and 1 6,500k. PAR with new bulbs is around 200 in the sand and 300-400 in the whole tank. At 12 months I've noticed about a 20-25% decrease in PAR and about a 30% total PAR reduction at 18 months. What I've noticed is that the big decrease in PAR is in the first 12 months, after that you could easily get 2 years out of a bulb without losing much par but the main concern at that bulb age should be spectrum shifts.
I love LEDs but recently I tried achieving the same par results over my tank with 3 XR15 G6 PROs and at 100% intensity, they only hit about 100 par at the sand. I took them down and installed my T5s again. You could probably achieve the same PAR results with maybe 4 or 5 XR15s or 2 XR30s but now you're looking to spend around $2k+ in lighting.
Market trends are trying to stay away from T5s, maybe because they don't own a T5 company yet, but people on a budget should seriously consider them.