I would for sure expect any less than super premium widey to be a bit soft wide open. I have never owned a wide that wasn't. For landscape and street shots I generally shoot at minimum f4, more often 5.6 or even 8 depending on the light. I have had Canon L's (multiple copies of the 17-40), Zeiss, Voigtlander and all needed stopping down for best results. I'm sure there are some who will counter that and they're entitled to their views, but have a look at any wide open shot they use as evidence and I mean in its RAW form. I just think it's a little in the nature of the beast. Widey lenses don't have that critical sharpness you get with say a classic 50mm design. The 20-35 is the same. Really, I'd say only my Zeiss 25mm 2 was anywhere close to 'sharp' and constrasty wide open. Even then the corners tended to be soft until stopped down. That's a £1200 lens. So there're two possibilities. The first is that for your budget you may have unrealistic expectations. The solution is to decide what is a fair expectation and work with that, or selling it and saving up maybe £600+ and getting something better. Second is you do have a duffer. You can only post some shots on tripod, remote release at say 2.8, 4, 5.6 and 8 to judge if what you get is acceptable. If there are clear focus or displacement issues then get a refund. You want a nice shot in good light with verticals and horizontals across the frame and then do some simple PP on it and then judge. You should get good sharpness and contrast with minimum effort. If you can't get that then it's probably not right. Lenses you have to enjoy and want to use and trust to deliver. If you don't feel right with one I always think better get rid. But I also think, from experience, every lens needs to be properly tested before judging. If you do that you can feel reassured you've given it its best shot. I've always been fine with my copies and I'm very particular. But I'm also aware that any cheaper lens means compromises and because I'm not a big wide angle shooter I prefer not to spend too much and so accept them.
I would be happy with those. It does depend if they're centre of the frame and whether you're shooting at 20 or 35mm, but broadly I'd say it looks OK. The 17-40 L was one of my favourite lenses when I shot Canon but I went 20-35mm because I just so rarely used it but still wanted something decent in my bag. From memory, I mainly shot 5.6 with the L. It's clear where the sweet spot on your 20-35 is and so I'd use it between f4-8 if it was mine. You have good contrast there. A good thing about this lens is the build and feel and for me it's a lens I've enjoyed using. I'd be really surprised if another zoom up to £300-400 gave you anything better overall. You'd likely need to look at a 20 or 24mm type prime to stay close to your price band and get better results ... you'd still have to stop down tho to get best performance.
