I would try to look at these animes or merchandise from a bystanders point of view. Personally, I think beyblades are a superior product. Here's why:
Working in a toy store last holiday season, I had plenty of parents/grand parents ask me what exactly they were buying for there kids ALL the time. I've never picked up a beyblade in my life but I can look at one and tell you exactly how it's used and how their kids play with it. The toy itself is pretty straight forward. It's essentially a spinning top with a gimmick.
When it came to questions regarding Bakugan I always drew a blank. With someone of no prior knowledge of the show it's near impossible to glance at the product and wonder what exactly you DO with it. Is this a single toy you bang against eachother? Do you launch these at eachother? Granted, it's not the most complicated product out there, but it's not the easiest either.
As a consumer/child if you had to pick between the two at first glace, which would you chose? The toy that's easiest to understand and more accessible. The idea behind Beyblades is pretty ingenius, they're just marketing a flashy product that's been around forever and made a game out of it. Without fail my simple answer to the question what's a beyblade is a top. Is there a simple answer to what's a bakugan without ripping out a manual?
"Geech gone to heaven, Mr. Terwilliger."