Depends on what you're looking for.
If it's high-end mesh bodies, they're all over the place. You can find Adonis (outdated), Apollo (probably the current go-to body) and Ares (newer but less supported as far as clothes go) in every other freebie sim. You can usually find skins and hair there, too.
If it's a decent-looking but low-resource body, Roth2 v2 (successor of Roth 2.0 RC#1, now known as Roth2 v1, in turn successor of RothToo RC#1) was released a month ago. It's only available on RuthAndRoth (hg.osgrid.org/RuthAndRoth/142/104/22). Someone should really make this newest version known.
If it's clothes and accessories, your number one address is Klamotto (
https://opensimworld.com/hop/78282). Otto von Otter was a mesh clothing pioneer back in the day, and he has got lots and lots of stuff. Look for AlCapone menSweaR. You can find Otto's stuff on a lot of other freebie sims, but this is the current official shop where you find everything in one place. There are also other shops with e.g. entire avatars including Leora's Beautiful People where you may find current mesh avatars to base yours on. Furthermore, there's a big building just east of the sim centre where you can get just about everything and then some, not to mention teleports to other freebie shopping sims.
Another two good places for male mesh clothes are Taarna Welles' sims, Savvy (
https://opensimworld.com/hop/75031) with the reMake/reBoot shops where you can find most of her clothes, especially shoes, and the old La Baronnie sim (you can reach it and Savvy from here:
https://opensimworld.com/hop/74862) which still supplies additional shoes, eyeglasses and jewellery.
There's even more out there, and it's up to everyone individually what's "the best", but you can easily deck out a male avatar with only Klamotto and Savvy/La Baronnie.