At the risk of being labeled a SeXiSt, ATP. Men are just bigger, stronger, faster, and better athletes. There's only so much time in the day so I'm going to watch the better product. It's the same reason I watch the NBA over the WNBA. Granted I think the difference in ability between the ATP vs the WTA is noticeably smaller than the NBA vs the WNBA.
Always followed the men's game but increasingly becoming more interested in the women's game. I grew tired of the big three men years ago. The top 10 women is more fun because it is constantly changing.
Gotta be honest I’ll take an exciting women’s match over two 6’5” lanklets most days. The top men are still better to watch, but at the US Open I enjoyed Sakkari-Andreescu far more than Zverev Sinner or Opelka Harris for example.
I like the ATP when I watch tournaments in person due to the higher quality of play - UTR16s on the ATP while it is UTR13s on the WTA and the difference in level of play is shockingly high (mens college level for WTA vs mens top pro for ATP). I have done doubles drills against a WTA player who was in the final of the WTA season-ending tournament (she is ranked in the top 10 for doubles still) and the shot speed/pace is like high 5.0 men I sometimes play against, but she was deadly accurate and therefore better. I also see a few WTA players come and practice at my club against our club coaches (who are UTR 12 and 13) and it is not particularly entertaining for me. In contrast, when Nishikori, Verdasco etc. used to practice at my old club, the serves, movement and topspin was amazing to watch.
On TV you can’t really see the difference in level as easily and both ATP and WTA matches can be entertaining. I’ll pretty much watch any ATP tennis on TV - if it is WTA, I won’t watch lower-ranked players I’ve never heard of, but will watch if it is top players that I know of. I am still more likely to watch the WTA than other sports on TV unless the MLB baseball playoffs are on or there is a NFL game I want to watch.
Without consciously choosing, I find myself gravitating more to WTA. Not sure why, because I'm really turned off by the women that are overly vocal. Maybe think the speed of their game is more like something I can relate to.