23 gauge pin nailers have no head on them and offer little "compression" of the joints. I would recommend an 18 gauge brad nailer. The holes won't be that noticeable at all. I also suggest applying wood glue to the joint, then nailing, and if you can get some clamps on it then that would be better. Gluing the joint will actually hold it on its own, the nails set it while the glue cures and helps you align it.
Back during the black friday sales, i purchased a set of Home Depot (HDX brand) finish nailers, 16 ga finish nailer, stapler, 18 gauge brad nailer, and a 23 gauge pin nailer. I have build a few art easels as christmas presents with these. The 23 gauge pin nailer hole was not noticeable to anyone, the 18 gauge brad nailer was only slightly noticeable. I have used the 16 ga finish nailer extensively at home putting up crown molding and hanging doors. My experience with it is that it needs a little more PSI than the recommend 90 psi to bury the heads, it needs around 110 psi. But for the price (99.00) I will not complain. A porter cable or bostich will cost almost double that for a single gun.
You can still get the set that I purchased from the HD website, same price that I paid. I highly recommend this set.
Link:
http://www.homedepot.com/b/Tools-Hardware-Air-Compressors-Tools-Accessories-Nail-Guns-Nails-Nail-Guns-Collated-Tools/HDX/N-5yc1vZc2cdZ9tk