HBO Boxing is way better than showtime. This is because they get better boxers to box for them. Their undercards are also superior to showtime. HBO ever has cuter ringside girls. Another benefit to HBO boxing is that HBO has better other programming as well if you can only choose one channel.
Yes for HBO, no for Showtime. I will say HBO because it has superior quality boxing programming. And who can say they haven't enjoyed the commentators as well. The friendly old man we've all grown to love. Showtime is crappy in comparison. It's like comparing home made food (HBO) with McDonald's (Showtime). Though obviously Showtime does have some good programming.