What bike is the rack going on and what will be attached to the rack?
There are material differences. Topeak racks will be TIG-welded aluminum tubing. They're light and strong, but have less fatigue life. Eventually, they'll crack.
I have a Topeak beam rack and it's worked on two tours without issue. I've also used a variety of Topeak bags and panniers. Generally, I would assess Topeak as a good brand but not outstanding. It's a Taiwan-based brand that outsources 100% of its production to at least 70 different contractors, most of whom are in Taiwan and the rest in China. They are affordable without being cheap.
I have a Bontrager deluxe rack that is also tubular aluminum. I bought it for a specific fit to a Trek bike with disc brakes (Bontrager is Trek's accessory brand). I like it because it has lower side rails below the tire that I can mount Ortlieb panniers to and they sit far enough back to avoid heel-strike.
I had an Ortlieb Rack 3 rack. This one is also welded aluminum tubing. I don't think it's made in Germany like the Ortlieb bags, but I don't recall. It did not fit disc brake frames on two bikes I have, so it's been moved on, but it seemed good and had the lower rails I prefer for that style pannier.
I had a Tubus rack, the Cargo EVO. This one is brazed with Chromoly steel tubing, in Taiwan. This is a heavy-duty rack that will hold a lot of weight. It's been 'tested' to 88 pounds, but Tubus won't rate it that high because European regulations would then expect it to be suitable for a child carrier as mentioned above. I didn't like the way it fit my steel, rim-braked bike. It was too tall. So it's also been moved on.
Tubus also makes welded stainless steel racks, as does Nitto and whatever Taiwanese contractor Velo Orange uses.
Tubus also makes a couple of welded Titanium racks.
I have a welded solid steel wire rack that Dawes sold as a standard with the bike. It's a bit heavy but tough and fits perfectly. It's not ideal for modern clip-on style panniers, (it works but the bags rattle). It works well with the older style leather straps and spring-hook or the one-piece leather-strapped panniers that lay across the top like saddlebags on a horse.
So depending on your frame style and width, disc brakes or rim, and what bags or panniers you want to mount, you can find a good option, but not all rear racks are equal or compatible.