I've been riding 5.10 Impacts for many years. Never had any issues with the actual performance of the shoe, but the durability on the last pair was disappointing. Shoes started to fall apart after only 2 seasons (of light riding).
I've had great success with my Northwave winter commuting shoes, so I decided to try their flat pedal DH shoe - the Northwave Clan (which uses a Michelin rubber sole). Price is same as Impact so why not.
After a month of riding, I'm pretty impressed. The 2 major criteria I'm looking for are stiffness and grip. In terms of stiffness, its roughly on-par with the Impact. No noticeable difference.
In terms of grip, it's actually quite interesting. It's a different sensation than the insta-grip of the Impact (which as other's have mentioned, can be annoying when trying to adjust your foot to the right spot). Let me try to explain it - with the Northwave's when you initially put your foot on the pedal, it feels like it's sliding around all over the place. The initial grip is much less than the Impact. But once you get your foot in place, after a few seconds of pressure the shoe seems to "absorb" the pins, and you feel quite locked-in. Not quite to the same absolute extent as the Impact, but I'd say roughly 80-90% as locked-in. I've been riding in the rain/mud a fair bit, and once I get going down the trail I haven't had any issues with my feet coming off. It took me a couple rides to get used to, but now I quite like it. If I drag a foot in a corner or something, it's way easier to get my foot back in the sweet spot of the pedal, vs Impacts.
If your a rider who needs 100% maximum grip, I'd say stick with the Impact. But if you're someone who struggles with the 5.10's inability to allow for micro-adjustments to foot position, and you don't mind sacrificing a tiny bit of outright grip, I'd say the Northwave Clan's might be a good option.
One note - Northwave's fit is notoriously tight. Go up to a larger size from what your normally run. Seriously.