I've been wondering this for a while now. Both of them really made me feel special on the date I had with them. Blastiose just said his name a lot, or simply spoke a single syllable of it. Empoleon, however, has 4 syllables in his name so he REALLY "spiced it up"... especially after the date... but Daddy said not to talk about that part. Overall, I guess Blastiose was the best because of his frequent Master of Disguise references. No one will understand what I mean by that though, so maybe Empoleon is the best for you