It depends on your perspective.
with Montana, and Bangers, the effect is essentially the same for the first 5 pillz used.
so in theory, if you plan on using 6 or more pillz on a single card, you should go Bangers...
I always suggest using different Clan types.
poison.(note the lower case here)
because this gives your deck a Variety, but if you really like using - attack, then i suggest using Montana.
the only problem they have is a need to use pillz to gain the benefit of their bonus, especially when facing a - attack clan themselves.