Definitely, the 300 series offers the best bang for the buck in my opinion. They're great playing, great sounding, well-built guitars at a great price. Actually, I think the 3xxK series is the best value, but since those are limited editions...
Second would be a tie between the 500 and 700 series, which offer upper-end features at a decent price. Both series of guitars use traditional tonewoods (except cedar), and have the upgraded electronics (on "E" models).
But if I had to pick just one Taylor guitar to own, it would be the 614CE. While the guitar isn't exactly modestly priced, it offers a lot of features and options, as well as great looks for the money. The 600 series is a favorite of players who play live regularly, for a few reasons. First, these guitars look great on stage in their stunning colors and 3pc fretboard inlays, polished ebony headstock, etc. Second, maple offers better feedback resistance, which is a big plus on stage. Third, I've noticed that my 614CE seems less affected by temperature changes. (This might be a characteristic of the maple, or could be my imagination
). Plus, the 600 series comes with the upgraded electronics package with onboard preamp for ultimate control on stage. All of this doesn't mean that the 600 has poor unplugged tone. Exactly the opposite. The maple bodied guitars are loved by many, including myself, because of their excellent tone, and very even string-to-string response. I've played my 614CE live in front of small audiences on two occasions unplugged, and many people commented on how good the guitar sounded.
J.R.