Like brAin, I don't have any info on brand-specific gutter guards but I have something I'd like to share.
When you have the gutter-guard 'test' performed, remember that it represents a SEVERE rain. How many rains have you been in that feel like you're standing under the volume of water coming out of a hose in the small area they're testing??? I'd be more interested in seeing a test where they put holes in a bucket that simulates 1/2" of rain per hour that falls onto a roof. I understand that a roof is on average about 16' from rake to ridge and a bucket may not be able to simulate that volume but they should do something more realistic than lay a hose on a roof to simulate a 'normal' rain. Water from a hose that's under pressure is a lot of water and it will move almost anything off a roof, onto and over the gutter guards, and eventually onto the ground below leaving just water in the gutter. From what I've seen in my 'travels' is gutter guards that, sure, they keep stuff out of the gutters BUT you're still up there once or twice a year clearing off debris from either on top of the gutter or just behind it on the roof! So, imperically speaking, the guards DO keep debris out of the gutters but you're still up on the roof in late fall or early winter clearing stuff off the guards or just behind them on the roof. If you have the guards and don't keep them, or the roof, clear of debris, and you were to get a few inches of snow, well who knows. Water caught in the debis and freezing creates a barrier and so on and so forth.
I'm trying to discourage you but from my perspective, you can do a couple of other things first to mitigate the debris. Prune or remove problem trees. (Do one or the other.) If trees from neighbor's branches hang over your property line, cut them out. And lastly, since I know you'll end up on a ladder anyway each fall, flush your gutters with a garden hose just before the first freeze. And be sure the water flows out the downspouts cleanly. (They should be free and clear of debris too.) Now I could be setting myself up for some 'grief' by folks that have gutter-guards that work well. If anyone is going to give me grief, I'd be interested in knowing what type of trees you have, your roof pitch, how much debris is found on the ground that's fallen off the gutter guards, the number of different trees, how close each of them is to the house, and so on. At least this will give you AND me a perspective of how well they work in different 'scenarios'. I'll admit in advance that in some scenarios, they may work well and in others, they may not.