If you want to hunt and take shots out to ~100 yards, I would pick one with a relatively small dot size (3moa ish) and a wide range of brightness. Low brightness levels are very useful early and late in the day when a very bright dot and associated bloom will obscure a distant target
I would say to first decide which type of red dot sight you are most interested in, tube sights or reflex sights. If you lean toward tube sights, Ultradot has a strong reputation. Just pick which model suits you best. If you lean toward reflex sights, any of the top brands should be OK on a .41 mag, but adjustable brightness and easy battery replacement are important features.
Vortec Venom has a 3MOA dot, brightness settings, and a lifetime guarantee for approx. $230.00. Tube type use the Ultradot.
I just mounted a venom on a GP100 with a short wiggy rail. It is small and light and worked well at the range last weekend. 4" groups at 50 yards when leaning against a post with range loads. Dot size was reasonable and the intensity adjustment let me get down to a true 3MOA dot.
This is the second one I have mounted. The first was a floor model from Cabelas that I had to send back to be fixed because it didn't turn on (battery was dead when i got it and it was the only one they had on hand). They fixed/replaced it without question.
I ordered the second one new and when it came the threads on the battery cover were/got messed up (probably my fault) and the nut for the rail mount clamp was the wrong size and didn't engage the the threads. They replaced the cap and confirmed it works, and are sending a complete new base (couldn't tell me the thread size on the bolt) and threw in some swag for the troubles. Their customer service has been great, but I'm a bit surprised at the problems with this second venom right out of the box (who packs the wrong sized nut?!). I have several of their rifle scopes and a spotting scope and haven't had any issues with them. I am starting to re-consider the red-dots, but also feel they are a good value with a lifetime warranty and would happily purchase another should the need arise at this point.