hey Mr Juggler, I just was out using my about 25lb faster bike for a commute, and really from what you say ("maybe" some touring, mostly not) as someone who rides and owns the two types of bikes you say you are interested in, the lighter bike is always going to be more fun to ride--IF it fits you well and has the seating and riding position that you are comfortable on.
My lighter bike (and is by no means a light bike, there are tons of bikes in the low 20lb range, but for more money) is a perfectly capable light to medium tourer, so given that you "might" try touring at some point, and possibly go the light load route, a zippier more fun bike to ride unloaded or lightly loaded is certainly a lot of fun to ride.

so as someone said, you can always have a couple of bikes, but if that isnt in the cards, you've got my perspective that a lighter bike could very well work perfectly fine for what you expect to do.
cheers