I liked the ova more

You should start with the anime then the OVA. You'll understand more. And OVA might be more kick-ass but it was horrible of what they did to Seras. She has so much comic relief. BUUUT she was a real badass! So much cooler than the series. Only if the comic relief wouldn't ruin her so much... so anyway, you should start with the anime series first. Trust me. Don't listen to the people who say anime or OVA is better. They're only giving their opinions. You have yours. So just so you could understand more start with the old and end with the new. I recommend you take my advise. =3

The OVAs actually follows the manga so it is a much much better one to start with, it follows the manga very closely and how it was supposed to be done unlike the Hellsing anime. The OVAs also have way better animation, the Luke Valentine fight in the anime is pretty crappy compared to the OVA fight. I'm not saying you shouldn't watch the anime as well but OVA is the better one to start with.

the ova is better butthe anime explains alot