Just out of curiousity what precisely do you mean by smooth slow mo? How is FCP not smooth and Adobe is smooth?
FCP's time remap, used correctly, can provide you a slow motion effect. You can even work it to do a gradual increase if you want. The main caveat though is that at the end of the day you are trying to create frames that do not really exist. So image quality is only going to look so good. However, you can easily use a third party option like Twixtor if the FCP results aren't to your liking (but still stay with FCS).
All the NLE's have their strong and weak points. For off-speed cuts, I wouldn't swear off FCP over that. I would instead look for a camera that allows variable frame rates. If you can achieve it in camera, you'll beat any NLE or other software in quality because you actually shot the real frames, no math algorithms necessary.
i would check your frame rate. if you'r eusing 24p slow mo becomes hard to do in post. when using 24p, and if i know i want a scene to have that slo-mo look, i will film it every smooth and slow so there's no need to slow it in post. just a suggestion.
what I mean by smooth slow motion is that in AE smooth slow motion can be done by shot in 60 play in 24p and change the speed to slow as you want....my other question is that CAN SMOOTH SLOW MOTION BE DONE IN FCP6 ( DID THEY HAVE THIS FEATURE IN FCP 6) OR DO I HAVE TO SPEND ANOTHER THOUSAND TO BY AFTER EFFECT