I've used drop tuners and fives, and I think you might prefer a five. For tracks in D, a drop tuner is great, and I sometimes prefer it to using the low D on a five, but for tracks in Eb (and some other keys), I think a five is better. For a couple of years I played with a songwriter who often wrote in D and Eb, and I did fine with a drop tuner, but it would have been easier with a five. I bought a five after that band dissolved, and I've found them enormously useful, especially for musical theater shows. My M-2500 is just fantastic.
I also wish G&L would release some kind of P-bass fiver, either LB-105 or SB-15/25, because then I could replace my SB-2 with one and keep the herd at a manageable four, but it seems they've settled on the Kiloton as their single pickup passive fiver.