that is very tough. I had exactly the same dilemma a few months ago when my first SL60 was stolen.
I have always wanted a 911 and thought I might take the plunge with either a 993 or early 996.
I drove both (C2 tip cabs) and found that neither were as quick as the SL60. I didn't want a manual car. Clearly the 911 doesn't offer the same level of comfort as an SL60.
The 993's cabin in particular is very very bare and completely out-dated. As much as I love the 993 and 996 shape, they were simply not practical enough for me - no room for golf clubs!!!
In terms of depn, I think the 993 will hold its value better than a comparably priced 996. But the SL60 also seems to hold its value pretty well (far better than a new car of a similar value), and the 129 overall will, hopefully, come to be seen as a good value "semi-classic" car over the next few years.
So after considering the 911 I chose to buy another SL60. I don't regret my choice at all although deep in my heart in know that one day I will NEED to buy a 911, if only to get it out of my system....