Honestly, I'm not a fan of either, but moreso the template than the PrC. If you decide on the Disciple, the Hexblade makes for an excellent prefix as it grants you the spellcasting required, has full-BAB, Cha to saves, and has Know (Arcana) as a class skill. Here's a sample build that focuses on Str and Cha:
Hexblade 4/Ftr 1/Dragon Disciple 10/Blackguard 5
+17 BAB, 14/5/12 +Cha*2, Command Undead, 3rd lvl Divine spells, 1st lvl arcane spells, mettle, a familiar, Fiendish Servant, +1D6 sneak attack, Smite Good 2/day, etc.
At 8th level, I'd suggest
Hex 4/Ftr 1/Dragon Disciple 3, progress one more level in DD and then jump into Blackguard for two levels. After that, I'd go DD all the way and finish off the build with the final 3 levels of Blkg.
Either way...just my 2 cp
Edit: Ninja'd on the Hexblade!