In my opinion- the opinion of someone with little pratice on meditation and just some bare knowledge on general buddhism - is that actually you may start your practice slowly, without choosing exactly right now your path (and in the end, that path is very similar on many aspects i think). Be it Mahayana or Theravada, you still have the 4 Noble Truths, the 8Fold Path, Kamma concept, Rebirth concept, and Nibbana (i prefer the word "Nibbana", because "Nirvana" has a very strong mystical feeling, in a very Western way) concept. Also, you still have meditation techniques in both paths. Maybe in Mahayana one gives more attention to Karuna/Compassion.
So, why not still reading, studying and pratice things in a general way until you reach a much more strong feeling about your path?
Also, be aware that some schools may be apparently
very different from Theravada, like Esoteric Schools and Pure Land School, for example.
But Theravada is still a religious path. Buddhism is religion, whatever the school. Buddhism is not a philosophical way of life. Kamma (or karma) and rebirth, for example, are some of the concepts that makes buddhism a religion. If kamma and rebirth were scientifically accepted, probably we would say that buddhism was a way or philosofy of life, i guess.