I'll go with a mixed opinion. Bottom end wise the buick is a clear winner into the 11s, hands down. Stock short blocks have proven to take insane abuse. For instance, look at the rod on a Buick and a SBC rod. The point the buick starts costing you money is when you get into the idea of block girdles and billet caps. To a large degree this means that instead of spending money on a high bucks rotating assembly you're putting it into getting the block stiffer so it won't twist.
The valvetrain parts definitely go to the SBC. Buick rockers, shafts etc. tend to be a niche market and things are harder to get and more expensive. The minute you utter "roller cam" on a Buick you're talking $1200 if you want it to last at all. The other thing is that even though people don't end up with things like headers, inakes carbs etc. the cost is offset with a bigger turbo, etc.
Labor wise, I'd go with SBC hands down too. I'd bet there's a max of one person and/or shop to 30 in a Buick:SBC expertise ratio if that.
The still in production point is a good one too. As far as it goes, JY wise it's a trade off and dependant on your yard but here's my thought; To a typical rodder a 350 is a desireable engine, they get snatched up in a hurry. A 3.8 Buick is just not desiarble to the aggreate hot rodder population. This means you can have a pick and choose of a 3.8L block. The fact that heads are avalible easily and cheaply allows a person who's unfamiliar with it to attempt home porting a lot easier too; Which are you gonna be comfortable porting, a set of Brodix heads or a set you can pull offa a JY car for a Ben Franklin? What about the fact you can pull things like massive intercoolers off of diesels and fit em to the Buick for massive power gains.
The buick is a clear winner in another and often overlooked category of engine building; Electronics. Don't get me wrong, Carbs are fine and everything people have gone insanely quick with them. It's just that quite frankly, a stock Buick 1227148 box will tell you more about your engine then the carb EVER will. I've never seen a carb that would pull timing if you were knocking, nor adjust for temperatures or atmosphereic conditions, nor meter fuel as preciesly as a well tuned SFI system. The fact that you have the ability to tell when you're engine's being assaulted means you can beat on it without crushing it, as well as getting a lot more feedback to tune it. a $250 datamaster or a laptop+WinALDL+>$15 home built cable does what you'd need a fortune in Autometer stuff to do on a carb'd SBC and it still would only be close.
I guess my conclusion to this term paper (AKA rant) is *drumroll* that the buick would be the winner dollar for dollar, deep into the 11s. The buick is a far better street car, for a multitude of reasons. The aforementioned 3.42 rear end gear is a biggie. The fact that Alky injection is so practical and does so much on a Buick engine also speaks greatly, not to mention where people have gone on the stock turbo, headers heads cam and so on.
) and watch a bunch of "run-of-the-mill" grandma cars run 11's & 12's effortlessly...meanwhile, most of the noisy V8's (and I LOVE noisy V8's!) that obviously have lotsa bucks in them, go tear-assing down the track and barely run 13's!? 