Sorry in advance for making being repeating things that have been said already.
I like to think of myself as a proeminent deffender of the 9860 reputation so, here is my arguments in why you should buy yourslef a fx 9860 rather than the AFX2.
So, let's get started:
fx 9860 is the best calculator in it's class, if you do not require a computer Algebric system, then 9860 is the best choice and is not matched by any other calc.
In dynatech, they both cost 89€ so I guess price is not the issue.
9860 benefits from a Natural input display, which allows you to input equations, exressions in their natural form, and that means, for instance that 3/4 is not displayed as 3,4 instead :
.3.
---
.4.
This does avoid you errors input which are most frequent in inoportune situations such as a exam.
AFX doesn't, you have to input massive formulas into a single text line...
9860 has a perfectly contrasted LCD very crispy and defined, and white and black as colors, not dark green and light green like AFX, everyone who has one loves the screen.
For an extra of 30€ your 9860 comes with a SD card slot, which comes handy if you like me, like having all your things in the calc, with a 32 Mb SD card you 'll feel as if the sky is the limit about memory...
9860 benifts from a very faster processor than AFX, while AFX does a graph, fx 9860 completes 3 graphs, and in matrix operations it's 5 times faster. About BASIC programming, using a pseudo OpenGl developed by scratty, 9860 perfors nearly 10 times faster than an AFX in 3D programing.
Currently 9860 is the Casios's little girl, they are developing software for it, add ins, OS updates, while AFX2 is let's say left behind in development.
That's probably due to the fact that Fx 9860 is quite younger than AFX.
Fx9860 comes packed with a USB cable which allows must faster and easier communication, than the serial cable you have to buy (for 50€, or make if you have the skills, and the proper chips) for the AFX.
As far as I know, you do not have the geometry add in which allow you to create manipulate and animate geometrical figures, with a great interface and ease of use. Nor a e-activity aplications which allows you to integrate all the funtionality of your calculator in learning files.
AFX has CAS, that's true, however I guaranty that once a SDK is developed, we will try to port a CAS engine to 9860.
AFX has an already developed SDK, whle the 9860 is still in "development" proving that 9860 is a much newer calc. However in this very topic, we are making an effort for developing the a SDk, we have uncovered some of the machines hardware specs, including very recentrly the processor architecture and speed, you could check 9860 Reverse Assembling topic for that.
But now we have discovered (actually we were tiped off that 9860 uses a SuperH Hitachi processor by an unkown guest

) we can start our atempts to reverse the add ins and fully program the calculator, which thanks to it's Big fat RAM ( it posesses a 512 Kb RAM chip) and the fast 40mhz clocked processor can advance into some 3D features.
Kucalc, don't believe in the processor speed.. the O.S does all yesnod.gif . An HP 49g+ culd be squashed by an AFX (I did the benchmarking some time ago), Not talking about a 9860, it will destroy the HP lmao.gif . HP ARM9 runs capped at 75MHZ!!! (the max speed is 250Mhz on the original ARM9 cpu). How you explain it?? Simply, HP49g+ is a <insert f-word here>, That emulates old saturn 48g (1993!!!!!) architecture.
Actually the U101 oscillator the 9860 s processor uses, can be clocked up to 140 Mhz... it is scalable.
See my post on reverse assemblig relating to the U101 for more info ( it is on the first page of the topic and then follow the link on U101 in one of my posts...)
Now About TI
If you go for the Ti89 you will pay 150€ at dynatech and that's a good price... so it is out of the price range , and that alone should render useless arguments, nonetheless I am arguing

:
Ti 89 does posesse a Samsung 68000 ( clocked at 15 mhz) processor which is kind of nice, however running assembler code, it can not match the 9860 in speed which uses a SHC at 40 Mhz , and the super H architecture is far superior to the oldie 68000 , honestly my father, now he runs a civil construction company, but until he's late 30's (he's 50 now) he was head of the software department for a german/ portuguese informatics companiy named riemer, and he reacalls assembling for that processor, and it's predecessor 6800 and he says it was the most terribly concieved processor in his time. If you want me to ask him way I'll do it tomorrow, as he is asleep right now

)
Personal opinion of my dad apart, the Ti 89 is much dificult to use and terribly less user friendly ( I love repeating myself), it does not suport Natural text display, It posesses less Storage memory (not counting the Titanium edition) and a slimer RAM... it does have CAS and a more resoluted screen, and nativly suports 3D graphing , so it is your call if the 60 € difrence is worth it...
Edit :Jesus christ, I can't believe I wrote all that, I must have been out of my mind... sorry for you guys who had to read it...