DBX is my main explorer. And although the AspX is marginally better for this (better cockpit, bigger fuel scoop means more jumps per hour, arguably slightly better max jump range, can carry more stuff), the marginal advantages don't outweight it's annoying features - mainly annoying engine sound and more importantly, two bloody halogen beams shining right in your face all the time.
IMO, anyway.
DBX can also land anywhere, while Asp is at that size threshold where sometimes you're going to have problems finding a good landing spot.
I'd say keep the DBX for exploration. Take the money for the Asp and buy... I don't know... a Vulture or something. For combat fun.