... I guess some people read five chapters and decided they'd read the whole manga. First of all, the number of sex scenes mentioned has been grossly exaggerated by those who commented on it. Compared to berserk, this is much more toned down (and thank gods, the sex scenes bit in Berserk was really getting old). I'd say the ratio of sex scenes is maybe 1 (UB) to 10 (Berserk). And the ones in Berserk were also much more gruesome in nature.
On to the topic - you can obviously compare UB and Berserk. Personally, I loved Berserk initially. And still do, although IMO it has lost its way big time. UB, so far, seems much more focused - Koinzell wants to avenge himself and his three comrades, and that's what he's doing. Gats really had no reasons to save the people he did and slay the monsters he slew. Until his buddy came back from the dead, he had no idea how he might be able to strike back at him. Simple as that.
Koinzell instead knows perfectly who his targets are. I think his appearance makes the manga more interesting, not less. He doesn't look like a brooding dark swordsman physically, but if you READ the manga (don't just look at the pretty pictures boys!), you will see that mentally he is perpetually torn between the futility of it all, the fact he is killing heroes the people look up to... among other things. And as for his origins, we really don't know much (yet). We know what happened before he was slain, but we have no clue why he came back, or even what he truly is so far.
To sum it all up - do Berserk and UB have similar themes? Certainly. Is UB a 'bad copy' of Berserk? Not in my opinion. Is it worth a read? Definitely. The art is good (but then again, this is always very subjective...), and the story is as well. And, picture that, the story actually progresses instead of getting hopelessly lost in secondary adventures.
Not like in Berserk, I am sorry to say.