So first up, if all you want to do is set up mics and DI boxes and record instruments and vocals and then mix them, then reaper is an excellent platform. Like it’s seriously good. Great editing capabilities, more than capable fx, super flexible routing, etc. If you are looking to produce your songs, it will not be your bottleneck. I honestly can’t recommend it enough.
That said, as a songwriter, I prefer logic. Personally, I think logic’s drummer is worth the price of admission alone. (I know you said you didn’t have use for drums.) But from a song writing perspective, logic instruments are invaluable for sketching out instrumentation and arrangement ideas. In that vein, the score editor is useful for creating lead sheets or full scores for session players so they know what you want or the general idea of what you’re looking for. On the mixing side, logics stock plug ins and fx are excellent and match eq is quite useful in identifying differences between your mix and what you are trying to achieve. And if you ever decide to use Drummer, software instruments, or loops, smart tempo is super cool. This is just the surface, granted, but as a songwriter rooted in acoustic blues, there are many capabilities I’ve never had an inkling to explore.
GB vs logic? GB is great for getting started or quick ideas. And if you have an iPhone or iPad, it’s great for getting down song ideas and then those projects load in logic. Speaking of which, without advanced features turned on, logic looks and feels a lot like garage band except with more features and a mixer. So if you’ve toyed around w/ GB and like it but wish it could more, logic would be exactly that.