Good argument!!..me personally I'm with you on the TBOL,find it gives me better look than DBOL which just seems to give me a 'moon face'.
But...
Can understand your bros opinion,he will most likely look better on DBOL because of his stats so he has an argument especially if his attitude is what it us with regards to the quality of weight he's putting on.
Be father Xmas and get him some 50mg TBOL he will be surprised with his results even if doesn't tell you because he won't want to make you think your right!!