I've been asked the question of "which car should I buy" by several potential DIY buyers and my vote is for the 1988 non-turbo 240 or 740 (depending on your preference of body and interior). Here are my reasons:

Advantages:
1. Not plaged by the crumbling wiring harness issues of the 1980-1987 cars.
2. Of the LH-2.2 vehicles (1985-1988), it has the best fuel injection mixtures programmed into the 554 ECU (which can also be swapped into the 1985-87 cars in place of the 511 or 544).
3. Bulletproof LH-2.2 ECU, but any of the 511, 544, or the 554 ECUs from 1985-1988 fall into this category of an uber-durable ECU and I have yet to see one fail. I will not travel cross country in a non-turbo 1989 or later vehicle without a spare ECU as I've had too many of them die on client's cars to be considered reliable enough not to carry a spare (mostly issues with Pink, but I've also had two White labeled 951 units die too).
4. A minor item, but worth noting: 1988 is the first year that you can grease the U-joints on the driveshaft (after removing the metric allen set screw and installing a Zerk fitting).
5. Very common in the salvage yards (unlike the 1990 740 which has a lot of unique parts).
6. Improved K-Block engine in most if not all the 1988 and later cars (the first few off the assembly line may have missed it). The original 1985-87 B230 blocks are perfectly capable of long lives (I'm driving one now), but the 1988-1992 K-blocks received a much improved crankshaft with a better thrust bearing, and thicker connecting rods. (The piston slap issue remains the same until the 1993 L-blocks were introduced.)

Disadvantages of the 1988 cars that the later cars have:
1. No Self-Diagnostic system. (OBD-I is included on 1989 and later non-turbo cars, and 1990 and later turbos)
2. No Airbag.
3. No ABS on the 240 or 740 cars (optional on the 760 that year, standard on the 780).
4. 1993 B230 L-blocks have piston oil cooling jets that reduce piston temps, eliminate piston slap, and provide additional longevity to the pistons rings and cylinder walls. (I did a tear down on a 1993 240 block a few months ago that had 300,000 miles, and you could still see the factory cross-hatching on the cylinder walls, she looked almost new.)


Issues that I share with someone who is considering a turbo-equipped vehicle.
1. Take the planned maintenance costs of a non-turbo car and double it. A turbo car that's farther along in it's years will have a lot of fatigue of nylon, plastic, and wear items in the engine bay.
2. If you think you might need a replacement turbocharger (due to excessive wear or abuse), start shopping the salvage yards for a gently used one right away and you'll find one soon enough.
3. Carry a spare ECU that you know is good in your spare parts kit. Even if you have a blue labled one from 1985-1989 LH-2.2 I would have a spare as I've seen at least 3 of them die in the last 4 years.


Items I encourage everybody to have as a spare parts kit, for all rear-wheel drive 240/740/940 red-block engine Volvos. About $50 to $100 at a salvage yard can acquire all of the below listed items.
1. Spare Main Fuel System Relay (white) that powers the ECU and the fuel pumps. (On the 1988-1990 760 Turbo cars, this relay is Green and not compatible with the standard white relay.)
2. Air Mass Meter (not applicable for the 740 cars with Bendix/Regina/Rex systems)
3. Fuel Pressure Regulator (average life is 100,000 to 150,000 miles).
4. Overdrive Relay (white)
5. Spare 25 amp blade fuse (for 240 cars only, underhood fuse for fuel injection).
6. ECU if you have a '89 or later 240/740, or a 740/760 turbo 1985 and later.
7. Two quarts of oil, and two quarts of transmission fluid.
8. (suggested) A half-gallon or a full-gallon of engine coolant.

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, +300k miles.
'87 Silver 240 Wagon, 412k miles (wife's car).
'88 Black 780 Coupe, PRV-6, 144k miles.