I don't play this game but I just wanted to know since it's almost always the opposite
Even tho any% Is interesting Is too short i think. Personally 100% Is more challenging and requires more routing and other stuffs
As @Azmi mentioned, Any% is much harder than 100% due to a lot more precise tricks that are required to do during the run rather than 100% which more-so relies on skill and good RNG in very few places such as Furnace Fun and the Mr. Vile mini-game in Bubblegloop. Those precise tricks that I'm referring to are Bit Clips on N64 as well as FP Early, 640 Skip, 450 Skip, and if you're an Xbox runner, you also have Demo Desync Adventure (DDA) to consider too.
If you're wondering, Bit Clips are where you do extremely precise movements in certain areas to clip through the floor and enter levels without opening them. From what I've seen, the only levels that use Bit Clips are Mad Monster Mansion and Click Clock Wood. (Some also use Bit Clips for Bubblegloop Swamp, but not very often due to its sheer difficulty and high risk, low reward.)
Most people usually don't run any% because of the hardest trick which is at the end of the run, DoG skip (door of Grunty skip) which is very precise but skips 25 jiggies. Also any% has a long bee part (bee is difficult to control) where you go into 3 levels and do lot of glitches and precise stuff, not beginner friendly at all. There is any% no RBA without the bee but still DoG skip, and there is any% no DoG, but still a hard bee part. Also you don't have to do bitclips to run these categories until you're a top player, there are routes without which are slower (for exemple any% no bitclips WR was a 1:06 so 7 minutes slower). But yeah 100% is definitely easier, lot of beginner strats and routes, and not lots of glitches in them.
btw it is really possible to not start with 100%, i personnally started with any% no RBA. Just you have to be interested in doing glitches if it's the case. It's really easier than any%, you can do the old route (WR was a 1:14 by azmi), there is also an older easier gobi's valley route than he did, you can look at my old 1:17. Just learning FP early and DoG skip can be frustrating, you also don't have to do TTC early as a beginner so take 2 more jiggies.