Therein lies the rub. I like the way the older necks feel, but the five piece ones with the volute are more sturdy. A neck crack would be deal breaker for me. I'd keep your 1451!
I'm late jumping in here but I have to say something about the very common neck cracks on rear mounted locking nuts...
Often they effect tuning and structural integrity not one bit. I have a 1990 RG550 that has a V shaped crack at the bolts and have had no trouble with it whatsoever (the crack has been there, and has not gotten larger, for the past 10 years or so... appeared after I threw the guitar)
I had someone bring me an old 570 that had the same type of crack, but had tuning instability... everything else was okay on the guitar so I assumed it was the crack causing the problem.
Did some research on how to fix it, and while a little scary to pull the wood back a bit to get the glue in, after the glue set and the wood sanded smooth; the guitar was as good as new with only nominal tuning glitches (no more than you expect on any guitar) so the repair was a success.
Don't write off a guitar because of this crack, if it's bad it can be fixed, if it's minor you won't even have to worry about it. I'd use it as a bargaining point to get a lower price though.
One more point; I knew someone years ago that broke the headstock OFF of his Les Paul.
It was a clean break, almost no splintering... a couple of dowels, a drill and quite a bit of glue and he was back in business.
Just about anything can be fixed. Wood glue is an amazing thing and glued wood is usually stronger than a solid piece. (That's why Ibanez makes their necks with multiple pieces of wood, you know.