Having played (and owned) nearly all the current models (T4 excluded), from my perspective, the drums on the Roland's and Audya seem to be about 20 to 30 percent louder than Yamaha, and a bit more harsh. And that's right out of the box.
Now, with only some minor tuning, if you wish, you can make the Yamaha drums just as loud as Roland's, but it takes a bit more work to make them harsh sounding.
Keep in mind that in all likelihood, the vast majority of keyboard owners DO NOT know how to tune their arrangers. I've communicated with players who have owned their boards for 5 years and never knew there was a mixing console, or a global EQ that could be tuned and saved as default. I've posted detailed instructions on how to create registrations and received PM thanks from hundreds of individuals that were completely unaware how to save specific song settings using the keyboard's onboard tuning features, all in a single registration.
All of this takes time to learn, and in this world of instant gratification a lot of folks are not willing to crack open the instruction manual and figure these things out.
For those of you who wish to hear all the keyboard's drum kits, I strongly suggest hearing them live--not a recorded sample over an Internet site. Spend the time and money and travel to Gorge Key's or Frank's stores, or if they're too far away, how about just visiting the nearest GC. Listen to the drums through the same sound system, and do it before and after tuning--there is a difference.
All of this, of course, is very subjective. Some players, and their audiences, enjoy the sounds of more subdued drums, while others may like them loud and harsh sounding. It's all a matter of personal preference, and as in many instances, there is no right or wrong, good or bad. Yamaha does it their way, Korg does it another way, Roland has their way, Audya has their way--all of which can be considered individualistic attributes of each particular manufacturer. If you like what you hear--buy it. If you don't like what you hear--don't buy it. It's that easy!
For me, personally, I try to keep an open mind about these things, therefore brand names play very little role in making a decision of which keyboard to use, or buy. I have a four-day open slot this month, during which time I'll either go sailing, or if the weather's nasty, drive to New England and look at a T4. To be perfectly candid, I'd rather go sailing.
Cheers,
Gary
The edit was for a spelling correction.
[This message has been edited by travlin'easy (edited 10-05-2010).]