Since this is one not for the faint of heart, I will give the warning up front.
No matter if you watch the original or Ultimate, they both have gore and rape/sex so please be aware. One has it more than the other, with the raping/sex though. (The original.)
Ok, I love Hellsing and I liked the art for both the original and Ultimate. I think the thing that annoyed me the most about Ultimate was that you couldn't see Alucards face a lot. It was dark faces in the Ultimate series. I have to admit though. They looked better in it. Except for Integra. She looked like a dude. That wasn't very appealing. I did like the action though. I enjoyed the difference in endings. Since they were so different.
I feel like I should make a review for the original all on it's own.
Anyway, Blood and gore everywhere. If you don't like that stuff then you won't like this show.
Alucard is very enjoyable to look at although he is mostly shadow all the time. When he turns into his 'original' form... He's nice. ;)
Seras is much more of a main -beat-em-up- type character in this one, which is wonderful.
Like I said, The story goes completely different in this so if you haven't watched it and you have only watched the original... please watch this.
Lots of different characters but also characters you know of from the original show.