I have used the ai98 for a year and just starting using the Tour F. I agree with the comments above and I am finding more control and accuracy with the Tour F. It is stiffer than the ai98 but not at all uncomfortable. The tour f is a nice update to the Tour 97 which was my go to racquet for a long time.
Not exactly apples for apples, but I got the Tour F 97-310 and the Ai98 Lite on demo from TW.
FWIW, I'm old-school, all-court, old fart, 4.5+, who tends to not rely on all topspin all the time, and likes smaller, flexier, heavier, lower powered racquets.
Last three racquets: Volkl Tour 10 Mid, C10 Pro, IG Prestige S, all in the 12+ range, but getting lighter with each iteration.
Since I ain't getting any younger, I've been moving towards lighter player's models, which led me to the IGPS. Generally works---way better for me than the vitriol that some folks in this group spew at it---but always open to options.
Intrigued by the specs of the Tour F 97-310, but was wary of the 66RA stiffness.
Spent 1.5 hours with a ball machine yesterday. I'd tried the non-Lite version of the Ai98 a couple of months ago, based on all of the hoopla. Didn't gel with the standard one, but the Lite version felt and played better. Maybe the strings were fresher this time around. Don't think I'd change to this, but it would be a good option for my wife. Since I'm not as interested in it as the Tour F, I didn't spend a ton of time with it. Not bad though. Beam is not my preference.
Generally pretty impressed by the Tour F. Swings easy, the stiffness didn't bother me, plenty of spin, even with 21 crosses, power a bit higher than the IGPS, decent sweet spot.
Only thing off-putting were the strings, which are the new Yonex neon green like the old Prince Syn Gut, as it clashed with the PJ, and a bit of string ping with no damper. PJ might be a little "too young / hip" looking for an old fart like me.
Will take it out a few more times before returning them to TW. I could see myself changing to the Tour F, with a few mods ( leather grip, poly / syn gut hybrid string job, maybe a bit of lead ) , but stock was quite nice.