I'm going to stick my nose into this.
1st, I own a '93 so I'm biased.
After reading literally over 1000 posts from Allante owners of all years I've come to the conclusion buying a low mileage '93 is the only way to go.
Reasons:
1. No droopy visors! Seems to be a big problem in older models. The '93 uses Eldorado or Seville visors so replacement is easy to come by whereas older Allante's used a unique visor. Replaements are not available to my knowledge.
2. Northstar engine (parts availability excellent)
3. The tranny (best of all years produced for Allante); an excellent performer
4. The seats. Controls are straight forward unlike the Recardo's; 3 switches instead of 6 or 7- too many to go wrong. '93 seats are full leather Eldorado seats so all parts readily available in junk yards cheap.
5. Northstar engine (doesnt' require the critical care as previous years)
6. Brakes. Standard Cadillac disk brakes. Older years are VERY costly to maintain plus finding someone who can do the job right isn't easy. Any brake shop can take care of '93 brake system.)
7. Cupholder in center console (most everyone who owns an older Allante wish they had that feature.
8. Speakers. Not Bose but standard Cadillac. They do not have the multi-amplifer replacement problem that is common on all previous year models and quite costly to repair.)
9. Northstar engine. More HP than all previous models.
10. No vent windows. (Cleaner look)
11. Exterior lighting system. (Less complicated than previous models)
12. The seats. (Personal opinion. I don't like the looks of the Recardo seats; especially if they have that large plactic loop guiding the seatbelt. I don't like the plastic seatbelt retractors on the the '98 and newer Sevilles either.)
13. The headrests. Two way adjustable. They also kinda match the overall appearance of the Allante which to me is square-ish. The recardo headrests are curved which don't really match the square corners of the interior. Again, personal opinion).
14. The seatbelts. (I hate seatbelts when they don't fit over me properly. On the '93 they fit perfectly! Very comfortable. Plus they don't hold you to the seat if you want to move forward or reach to the passenger footwell.
15. The Northstar exterior emblem treatment. (Still seen on today's Cadillacs)
16. The top cover. (Personal opinion: I like the looks of the domed top cover vice the flat deck cover, or sculptured looking cover.)
17. Older models are more likely to have split, discolored or curled dash on top.
18. Pre '93s seem to have a problem with soft top wearing a hole on either side just aft of side windows.
19. Some '93 have color matching tops. I also like the material used on the '93 tops. Its cloth like. I honestly don't know if the same material is used on older Allantes.
20. Suspension. If you like the basic Cadillac ride, the '93 duplicates it quite well in the city but stiffens up nicely as you move past 40mph. The car is VERY stable at speeds above 100 mph. Actual top speed on the '93 is 145 MPH. I don't know about earlier versions.
21. The Northstar engine. It was an Indianapolis Pace car and was the only pace car ever (up to that time) that did not require ANY modifications to the body, cooling, engine or brakes before going on the track. Pace cars must be able to take the cars around at ~120 MPH before they hit the starting line.
22. When the '93 was designed Cadillac did not expect it would be the last year of production therefore their latest technology in electricals, suspension and powertrain when into it.
23. The wheels (I believe early models had 15" wheels). Only the '93 had the factory chrome wheel option.
24. I installed the SuperChips super chip and a K&N filter which raised the Northstars HP to over 305; possibly more.
Some people like to say the '93 was slightly cheapened by the loss of the BOSE system and the replacement of the Recardos with standard Eldorado seats but its my opinion that only reduces the longterm maintence of the vehicle by the fact that parts for those items are readily available and cheaper to replace/repair. I guess its a tradeoff.
Remember, I'm biased towards '93s because its the only Allante I've owned, but I've owned many Cadillacs over the years and this one so far is overall the coolest one of them all (the '62 convert w/buckets seats is a close second though).
Since I became an owner only one year ago I've had no serious issues or repairs required. I've had to replace the rearview mirror but that was at no cost. I had to replace the CD player but that is common on older Cadillacs and Buicks (they used the same model).
Overall I have absolutely no complaints.
My brother has owned 3 Allantes; an '89, a '90 and currently owns a '93. If you asked him I believe he'd say his favorite was the '90. He bought it new off the showroom floor at the time.
Scroll through posts at this link
http://www.allante.com/discussion_frm.htm
You might begin to see a pattern emerge that fits your liking, or not.
..rickko..
Re: Best Allante to buy? 
I live in Vancouver BC. This site has been a great help in deciding what year to buy. After reading all the info, particularly in this thread, I decided on the 91/92. I am already looking for a hardtop for the car as we get a fair amount of rain here. My first question to all of you is will the earlier tops fit my car because of the different latches?? 
