I'd personally go for the MSI. I've got a sapphire 3850 that runs quite well, and I bought it after the Power Color 3850 arrived with bad memory. I don't have any experience with HIS, but their cards tend to run slightly higher in price from what I've seen.
I'm just chiming in here, but strangely enough, I rarely ever see bad reviews of any ATi products from any company. With Nvidia, you see a lot more...at least that's what I have noticed.
I have been using MSI products for a little while now, I really like them. Good support. I'm really leaning towards buying a 4850 today as well, and right now, though I'm leaning towards the Powercolor or Diamond card.
i've had visiontek ati cards before in the past.....
my first graphics card ever was a 9100 - works fine till this day
2nd was my x1300 pro, which died on my old AGP system after 3 months of use, so i replaced it with a 2600 PRO, works well till this day, but my warranty expired on the x1300 so i couldn't get it replaced -sad- 2:1 with visiontek
i have a sapphire 3870x2 right now, works fine, OC-ed a bit and it runs like a charm. i haven't had bad experiences with sapphire because mine works fine, but i've heard and read about that sapphire's support suxz0rs.
so i guess in the future, i probably won't get another sapphire card just because of the customer support reputation. what i look for in a card is customer support and warranty and such.
i think every card should run fine given any manufacturer. they are out to do business and their products can't fail or else they would run out of business...
i value nice friendly customer service the most...so i suggest look into that and compare how each company fares with one another.
I prefer MSI products over anybody else, but unfortunatly my current rig does not consist of an MSI product. And my 2 4850's on the way are Sapphire's, FX did not have the MSI ones up yet. Im currently trying to contact Sapphire about their Vapor-X cooler on these cards, but I could be waiting a while as ive heard Sapphire customer service is non-existant. I might actually not open these cards and sell them for MSI ones.
As far as HIS goes, I would avoid them like the plague. Ive had a HIS 2900XT and a 2600XT crap on me. The 2900XT was by far the worse case of bad card that ive personally seen, it was so bad there was video corruption in the damn BIOS and boot up.
Personally I'm not buying Sapphire again, their cooling solution for the X1950 Pro I bought simply sucks and my older Sapphire 9600 Pro started artifacting on me just a few months after I bought it. Their support was useless.
So my 4870 will either be an MSI or Visiontek, probably MSI.