"What is your IBA ride preference?" is a fantastically open-ended question - one that has a myriad of answers. Like, a few thousand of them, I'd bet.
@Ira is right. Yet, there may actually be an even easier means to find the information that the OP - or anyone else - might be after.
Once you get past the basic SS and BB rides, you start stepping into 'rarefied air', as the types, styles, and lengths of rides becomes quite large. See here:
https://forum.ironbutt.org/index.php?threads/different-named-ss1000-rides.1912/#post-25337
Before I did a 48 State ride, I really wanted to have an idea of the _best_ month to do that ride. Well, half-a-month, since it only takes 10 days - plus a couple more to get to my starting point and to get back home from my ending point.
A couple of hours of analysis gave me my answer, and with a little more effort, I was able to decide a good time to do the ride. Life got in the way, and all of my plans on when I was doing that ride got canned, and I got to do the ride a few weeks earlier.
Now, one of the points I'm really big on is the
how in the hell did that ride get started? history of many of the themed rides have. Some of this history is captured in the ride documents listed on the IBA Ride List, and some are only known from this forum - and from the prior version of forum software that used to exist. There has been efforts to capture this history (great!) simply so the story behind the ride doesn't get lost.
Thus, once you know the history behind a ride like the Why? to Whynot!, the
Atomic 1000 or any number of rides offered, it becomes a goal to tick that one off the list.
Might I also suggest a bit of reading thru the archives that the
Motorcycle Tourer's Forum has to offer.