I started out with a Feather for much the same reason that you stated. I was interested in a better shave, and drawn to the idea of using a straight, but not sure about honing, stropping etc.
To answer your question, I would say that your results for a one pass Feather shave will be better than with a disposable. Closer, less irritaion etc. Obviously, a multi-pass Feather shave will be quite a bit better. This assumes that your technique is up to the task, because I will tell you that a Feather is not hard to use (super light pressure is key), but it is very unforgiving of sloppy technique.
In my opinion, both the Feather and a conventional straight will yield BBS shaves, no problem. However, I find that a shave with a conventional straight lasts longer and I enjoy it quite a bit more. The whole process that I was unsure of in the beginning has become a lot of fun for me and I prefer the feel of a conventional straight by far.
In any case, dump the disposables and cartridges. Even if you went to a DE, or better yet, an injector you would be making a big step forwards. And, when you're ready, the straights and SRP will be here for you. You've got a lot of shaves ahead of you, so you ought to learn to enjoy them.