Customer reviews of SPD to Crank Brothers isn't really a fair comparison. Shimano-style SPD mountain pedals are used by orders of magnitude more riders than Crank Brothers, so it's logical that SPD would have more advocates. In courts of public opinion, the majority opinion usually wins, even if it's silly.
The two different Look adapter sets (
Wellgo RC8,
Crank Brothers 3-hole cleat) include both 3-hole adapters and cleats, but they cleat to entirely different pedals. You choose the adapter system to mate to your preferred pedals. The Crank Brothers adapters can fit SPD cleats, but the Wellgo SPD adapters don't look like they'll accept Crank Brothers cleats - or Time ATAC cleats, or Speedplay cleats, or Bebop cleats, all of which have larger bases than SPD. The Wellgo adapters look like they're molded to fit SPD adapters, and nothing else. Actually, it looks like they've disassembled the regular Shimano SPD cleat into two parts (the brass horizontal bar and the underlying silver top/bottom lobes). If that's true, then that's super-awful; it means that you won't be able to buy regular SPD replacement clets, but you'll have to buy special weirdo cleats from Wellgo - which will be available only for as long as Wellgo chooses to make them available. Ecch.
I'd really like to be wrong about that, if only because forcing people to buy replacement parts from a single manufacturer is a generally bad thing. In Wellgo's case, it would be a case of spending extra money to lock people into the replacement chain; Wellgo already makes
standard SPD cleats (98A), so the expense of making an nearly-identical cleat seems pretty wasteful.
The Crank Brothers adapters are a sort of nylon. I've been a CB rider for years, and I hoard the discontinued Quattro road pedals (for which the 3-hole Look adapters were originally designed). Since CB uses the same cleat for both mountain and road pedals, I normally ride the Quattro pedals on my daily rider with mountain shoes, just because they're easier for walking around. I've got a set of road shoes with adapter-ized cleats, but they don't get a lot of use; like other bulky road cleats (Look, Time, SPD-SL), I wouldn't want to duck-walk around in them, for fear of slipping and breaking my butt-bone.
From the Amazon photo, the Wellgo adapters look to be metal, but they don't say. Wellgo is a Taiwanese OEM company, and their English site has no information about the RC8 at all, aside from the image. Obviously, if they're metal, they'll last longer; but who knows?
If what you need is a 3-hole shoe-to-2-hole cleat adapter without the cleat, Sidi has one:
I don't think this is really a "which adapter is better?" question; I think this is really a "which cleated pedal system is better?" question. That's a very individual question, which is hard to answer except by direct experiment. My own first attempt with cleated pedals was with the double-sided platform+SPD system that (if memory recalls) was from Wellgo; they were cheapies from Nashbar about seven years back. I could never get used to them; I never mastered the technique of cleating in and out. I'd think I was cleated in and then my leg would fly out; I'd think I was cleated out, and I'd fall down with the bike on top of me.
Crank Brothers were comparatively easy for me; cleating in and out was a breeze. I now ride CB (older Candys and discontinued Quattros) on all my cleated bikes. I like the little bit of float they give me; I like the adjustable disconnect angle; I like the fact that I can use the same cleats on both road and mountain pedals. But that's just my own preference; YMMV.
My recommendation for anyone who wants to try cleated shoes/pedals, either for the first time or on a daily around-town bike, is to try SPD mountain shoes/pedals first. Since they're Shimano, they're more widespread than other systems; accordingly, they're widely copied (hello Wellgo and Ritchey!) and cheaper. If SPDs don't work for you, figure out why they don't work, and try another system that sounds like it addresses your problem.