i want a dense little nugget :)
it weighs the same, if you break it up with a grinder, it is the same amount so it doesn't really last longer, you just smoke less of it... when you have a more dense bud, you can put smaller pieces in your pipe and get the same amount of smoke /high out of it without packing it all the way full
it all boils down to personal preference, in the end if it weighs the same then its the same amount... and buying all your weed from dealers you almost never have a choice in the matter... if the type /density of buds is that important then start growin your own :)