MTU never listed the brand and model of the one they sold, so can't help there. I wish I could help, but my opinion and experience is laptops are too prone to failures (I know I'll hear about that one!!
).
I really can't see that an external drive is that much more equipment to haul and they usually will fit in the laptop case. I know...whatever the customer wants, but you know who they are going to come back to when a disk won't load right.