I am using and have used both. I currently have a 400w 12k Reeflux in the center and 250w 10k XMs on each side. I had been using 250w Reeflux prior to changing to XM.
I definitely like the 12k look, enough blue but not too much. I do however have 320w of superblue actinics so without those, you may like the 14k.
I had a Reeflux 10k 250w get hit with a water splash and cracked. It was about 8 months old. I was surprised to see that when I replaced it with my spare how yellow the older one (other side) had turned.
In addition, when I went with the XM bulbs I immediately had algae blooms. Seemed as though the XM bulbs had a lot more punch in them as opposed to the Reeflux. The 10k Reeflux were definitely more blue than the XM. The XM have a tint of yellow, in my opinion...........but you are not going 10k, just thought I would throw that in. I would expect 14k XM to be less blue than 14k Reeflux based on what I saw with the 10k bulbs.
Lastly and most importantly - the Reeflux bulbs sometimes will not fire up with a magnetic core/cap. type ballast. If you do not have an electronic ballast - they may not work. My 400w Reeflux bulb would not fire on my ballast or Philips. It was not until I changed ballast that I could use the bulb. I had no issue with 4 250w Reeflux bulbs, just the 400w and I was not the only one.
I have used both and next time will continue to go XM, just an opinion.
I have never used Hamilton so I can not comment on them vs. others.