Wow - big thread. I don't have time to read it, but I reckon it said that the 95 is the best 993 because of the OBD1 and the big valves and the 04 is the best 996 because it was the last of them and the IMS bearing was upgraded. I won't argue with that logic, but at the end of the day you have to buy the best car for the best price, and the year of manufacture should come second.
You are right in assuming that when the IMS bearing fails, the results are usually catastrophic. The engine sounds and runs fine until about 2 seconds before the bearing fails. If you are *really* sharp/lucky you will hear it and shut it down. More likely you don't hear it and the bearing fails, the cam chains skip, the valve train stops, the valves stay extended and the pistons smack into them. The engine will tear itself apart from the inside out. As ugly as it gets.
Problem is that the original bearing is factory sealed with grease inside. After about 60K miles the 0-40 motor oil seeps past the seals and washes away the grease. The thin motor oil doesn't have the right properties to keep the bearing lubed and the wear begins. 10K miles later the bearing fails.
The LNE bearing is an open design and the materials are designed to operate with the 0-40 motor oil. Problem solved....so they say.
I don't mean to freak you out. There are many 996 with well over 100K miles on them screaming all over the country. Contrary to popular opinion...they don't all fail eventually. Lot's of them are just fine. Just look at all the Boxsters parked iat the hair salons all over town, I find it hard to believe they all have new engines in them.
So please put it in perspective.
As far as finding a 996 with the LNE upgrade done, that might be difficult. So far there aren't too many around, and those that are were probably done by owners intending to keep their cars for a while.
Many other owners may not know exactly what their mechanic has done either...I have talked to a few people who say that they have had the bearing replaced when in fact they have only had the flange and seal replaced, or maybe even just the Rear Main Seal....that was another common (but minor) problem that has all been resolved now. Caveat Emptor...get proof of the claim!
The cost of the bearing is reasonable, about $700 although that may come down over time. The cost is in the labor since the trans, clutch flywheel have to come off. Of course this means that the best time to do the fix is when the clutch is replaced, at which point the extra labor becomes negligable.
What I did, and what I would therefore advise you to do, is to find a 996 which has had it's engine swapped out. When the clutch comes due, install the LNE bearing. I haven't had to do either of those yet, but by next year I'll be ready for that clutch I reckon. In the meantime I'm not worried.
In fact....the *absolute* worst case scenario is that my motor fails and I have to buy/build a new one. Total cost will be on the order of $10K - $15K and that is pretty much what I would expect to spend on a 993 motor rebuild should I have gone that route. People don't mention that the 993 motors weren't without their issues either and don't get me started on the pain of routine maintenance and minor niggling heat and oil leak issues that all air cooled cars suffer from to some extent.
One thing about Porsches....things can and do get expensive. I personally turn my own wrenches otherwise I couldn't play as hard as I do in this game.