While I have a little of everything, the majority of my spiders are NW terrestrial species. I started with those because they are easy to take care of, frequently out in the open, and don't have the potent venom of the OW spiders. (That said, I do have OW Ts as well now.)
I used to only have a few tarantulas (2 NW terrestrial, 1 NW arboreal, and 1 OW arboreal), but then I increased my collection for a presentation on South American tarantulas that I did for a Geography Day event at my local library. If I'm being honest, I didn't need to buy more spiders for the event - but it gave me an excuse to do so! That definitely left my collection heavily weighted toward NW terrestrials.
The majority of my collection (70ish out of 100ish) are African baboon species... so, Old World. They vary from terrestrial to fossorial to arboreal depending on the species.
After that, New Word Terrestrials would be next... Aphonopelma and Brachypelma account for probably close to a dozen specimens. Then have half a dozen Old World Arboreals (Pokies). The remaining few are scattered about.
As you can see NW have slight edge species wise over OW in my collection (and I'm getting a B. kahlenbergi this week making it 33 species. I've never really bothered to divide them by terrestrial or fossorial or arboreal.
My collection is spread even, and it’s weird because I don’t have a particular preference for specific genera. So, it was not self conscious, it just happened, probably because I’m more of a “That is a gorgeous spider. I need it.", kinda guy. I am considering expanding the collection into the world of non-theriphosid Mygalomorphae, because I’ve discovered some really cool looking spooders there.