Interesting question.

I've owned and extensively driven a PV, a couple of 122's (1 sedan, 1 wagon), a couple of 1800's (both 1800E), and a 145E. (And I currently have a 245).

Even then, it's a bit hard to winnow out a valid comparison. The cars were in different conditions, worn out, stock, modified, etc. I owned them at different points in my life, dumb teenager, 20's, 30's, 40's. Etc. etc.

Generally speaking:

1800: I've firmly fallen OUT of love with the 1800. I used to think it would be the best pushrod Volvo. But in the end, all it has going for it (as you'd expect) are the looks. Which are neat, even with the occasional awkward bit of surfacing (heh, the overlooked until the last minute transition of the round front fender shape to the vertical tail fin rear shape). But other than that, not that much to offer. They don't weigh less, they don't have better handling, they don't have more power, they have pretty dismal ergodynamics (special mention to the heater controls tucked underneath the dash). They have either common old Volvo parts or fairly unobtainable parts specific to the 1800. The drive isn't special, other than the view over the front fenders and hood. You sit in it with the windowsills up very high. Nobody, not even kids (once a child seat is there, there's no leg room left over even for a tot) can use the back seat, it's a Euro tax dodge. They rust easily, and are very hard to fix. Meh. The performance just doesn't live up to the looks. I still think they're neat in concept, but that's about it.

145: Definitely a more grown up car. More room inside. Quieter. Slightly more solid suspension with a bit more isolation. Great brakes. Great visibility. Like any old Volvo the handling is pretty good once you've tires/wheels/shocks/springs/sway bar'ed it. It's a bit heavier, so it's a bit slower. Only thing I'd say is an entirely objective detraction is that it's basically a 60's car without the cool 60's styling to go with it. It visually blends in with the 240 for the most part. Entirely objective, but I sort of want my old car to look like an older car more than the 140 does.

122: Def. has the cool 50's styling. Which is half the fun of driving an older car (for me). It's bigger than a PV inside. It has a smoother suspension. It's a little heavier than a PV, but with that you get quite a bit of added safety. Built or practicality, like the 140 great visibility inside and room for regular sized people inside. I guess I don't need to tell you much about the 122, you had one.

PV: Of all the old Volvo's I've owned, I've like my PV the most. I'm not entirely sure why that is. But even when it had the tired 85 HP (if that, it was worn out) B18 in it, skinny tires, worn out shocks and a skinny stock front sway bar it was somehow just a bit more fun to drive. Part of it is certainly the weight, 2200 lbs or so, it's like having a couple of people climb out of your 122 that you didn't know were there. Part of it is the pre-war 40's styling. A 60's car with 40's styling. Heh, like I said, if I'm driving an old car, I like it to look old. This one looks a couple of decades older than it actually is. There's less room in a PV, the 40's style body is narrow around the front seats - and it tapers forward of that with just enough room for 3 pedals in a narrow footwell. Maybe a little snugger in the rear seats. The visibility is a bit on the poor side out the rear - the rear window is comparatively smaller (even on the later cars), and it points up at the sky, you won't see much of anything out of it. The light weight makes the most out of whatever HP you have under the round hood. The suspension can be a bit harsh, as 3 out of the 4 front suspension bushings are metal on metal (lots of grease fittings), but it seems to have a precision and feel that's better than the more rubber isolated later cars. The lighter weight probably helps there too, but the whole thing just has a more spritely feel. Safety wise.... well, it's not good. The PV weighs less because it has a lot less structure to it. It predates the Volvo focus on safety, for sure. Although the 60's cars have seatbelt mounts, including front shoulder belts, it just doesn't have the overbuilt passenger cage of a 122. The steering column is a straight metal pole that extends from the steering wheel up to the steering box, just a couple of inches behind the front sheetmetal. I guess you can rationalize that it's safer than a motorcycle, that's what I do.

If I was going to buy another old Volvo, I'd buy a PV in a heartbeat. Not that any of the others are bad, it's just that the PV is better. It feels special. It's funkier and lighter on its feet. It still makes me smile after 15 years of owning the silly thing, every time I as much as start it up to move it around the driveway (those snorty DCOE's and that loud exhaust).

Well, I'd also like a Sugga and maybe a Duett (those are so different from a PV as to not quite qualify as just another PV body style) too.
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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)