The giantbomb SWTOR guild has quite a few 50s at this point. I'm sure dudes would be glad to run you through your main story quest so you could at least see that. Finishing up act 2 (Hoth) and act 3 (Belsavis, Voss, Correlia) while only doing critical path class story missions would probably take less than 5 hours. The sith warrior story has a definite ending and is worth finishing.
Just hit up Kessler run chat I'm sure you could get power leveled through your story. Hell I'd do it if you wanted. Whisper Trollius on mind trick.
I would say from a gameplay perspective 2 was much better. However I liked the first one's story and presentation better plus the reliable structure. You go to a city, gather evidence, do side missions, then initiate assasin memory and go to work. In the second one I couldn't really follow anything, I never really knew who I was going after. It lacked story focus. Gathering intel on your target in the first one gave you a better sense of purpose and background that the story in 2 lacked. But in 2 the hiding in crowds mechanic, the feel of the assasination, the combat, and the world movement were all better. So 2 had better raw elements of gameplay but 1 put it together better.