Well, I owned a CL600 with a bunch of Renntech upgrades, with every option. Car before Renntech stickered at $139,500. I drove at least half a dozen CL55's and SL55's. I spent some extensive time in 996TT's as well, finaly buying my 05 NSX.
The 996TT is a great car. Fast. Relatively comfy. Decent all weather capability. Practical actually for a supercar. Holds is value well, relatively reliable. It was just too common for me. Its a 911. You may know its a turbo, but to most eyes, its just another 911 and everyone has an opinion on that car it seems.
The CL is a powerful car. Extremely smooth. The fit and finish and materials quality is a whole level beyond the Porsche, nevermind the NSX which in comparison honestly, is just.... cheap. It is a car that is so quiet and smooth, so safe, so powerful, you feel like you are in charge of a locomotive on the road. When I was tired after a long day, I wanted nothing more than to get in my 600 and drive home.
The CL doesn't get enough credit for what it is, because not many people have experienced that level of quiet and sophistication in a car. With the double pane glass up, I could not hear cars pass within 2 feet of me. It is also, probably the safest car on the road. It sucks its doors shut, it has a massage feature in the seats, the rearviw mirror is motorized. Full active suspension. It gives you total isolation from any sort of nastiness outside.
But that isolation is good and bad. Good, if you want to be isolated. Which when tired or on a long trip, or in traffic, is exactly what I wanted. Its a cocoon like no other. Bad, if its a nice summer day and you are excited to "drive", there is little feel or feedback. Just not that FUN.
If it were my daily driver, I'd have a hard time choosing. It depends on the roads I had to travel in, etc. The NSX is actually my third car now, so I wanted something "fun", and I have more fun in this than anything else.
You cannot beat the NSX in terms of reliability or depreciation. Look at the hit the CL has taken. Its a great bargain now for the amount of CAR that you get. No doubt. But be ready to take a hit still.
You need to drive one. If its not for you, then like Vance suggested, I really would consider going to an 02+ NSX. Then if you get bored, you can always supercharge it or whatever. You have a 91. I don't care what anyone says, there is a big difference in the 91 and say an 03. I wouldn't start pouring money into a 91.