There is a reason these are on sale at CDNN and at Davidson's (even cheaper!).
I would get the .44 mag. version.
Owned both, been down the .45 Colt road before, wouldn't go down it again. I have owned 3 RH's - a 20-year-old .44 mag. that was a tack driver like I've never owned since ... and 2 2001-era .45 Colts that I can't say enough bad things about.
Redhawk .45 #1 had stellar accuracy but was replaced because the action would bind and it wouldn't "revolve".
Redhawk .45 #2 worked properly but craftsmanship was crude and its accuracy problems were insurmountable. I guess I'm unreasonable about this but I expect a $500 7.5" barrelled revolver to do better than 5" groups at 25 yds. from a bench. A closer inspection revealed wildly varying cylinder throat diameters, all under .451". In all fairness to Ruger, I did not feel like sending it back and then waiting 2 months for them to possibly fix it, so off it went in a trade which ended up netting me a .25-06 Ruger M77 that I couldn't be happier with.
As for the .45 Colt, I've had a bunch of them over the years (mostly Rugers) and I have 0 now. Here's why I don't fool with it anymore:
1. Ruger can't seem to bore out consistent cylinder throats in .45. You'll have to pay someone to ream out your cylinder at extra expense, a big waste of time and effort. Most people don't seem to have problems with their new .44's.
2. The .45 Colt is a handloader's cartridge, expecially if you want to magnum-ize it. Why limit yourself like this unless you don't want the convenience of local availability or you just want to keep UPS drivers in a job. Personally, I hate UPS, so I want to be able to pick up my components at Wal-Mart 4 miles down the road.
3. Resale value is poor thanks to 1 and 2.
4. The magnumized .45 Colt is dying. Ruger's discontinued all of its guns that can shoot it except for the Blackhawk, so with fewer choices in guns we are going to hear less and less about it with all the .454's floating around.
While I personally believe the magnumized .45 Colt6 is better, I don't think any animal you shoot with it is going to know the difference between that and a .44 mag.
iF YOU still want a .45 Colt Redhawk, Davidson's has them on sale right now for $350. If you want the rings verson, I think it's $379.