I don't think any brands really stand out as the best these days, and I find that a lot of manufacturers older stuff was better. I think Nike are hit and miss, and Nadal's own line is particularly poor. I can't remember the last Adidas outfit that I really liked. I think Lacoste has too much going on with their Dimitrov/Fils line of clothing, and they're so boringly unadventurous with their Djokovic stuff, but when they try and do something different it's god awful like that purple and red one he wore at the backend of last season.
It's very subjective too at the end of the day. When I see an attire post on Instagram for instance with people commenting on who's they like the most, I never really find myself agreeing.
My favourites are probably some of Nadal's older stuff that used to contrast the colours well with the sweatbands/headbands, but my most favourite are Andy Murray's Adidas outfits. I just felt like they were super clean, but had something about them and used to contrast/match really well with the sweatbands too.