I wonder if there's any advantage to a stroked 2.8, like more hp or torque, as compared to a rebuilt 3.4 that's been bored .030 over. If not, I'd just go straight for the 3.4. It's set up for a crankshaft sensor in the event you ever wanted to upgrade to the 7730 ECM and it has better oiling than the 2.8.
The ARI 3.1 is built in the same manner as any 3.1 is built. It starts out as a 2.8. Different pistons and crank are added, to yield a longer stroke. It's the same way the factory did it, and the same way anyone else building a 3.1 does it. The 3.4 is a different story. It's that same "stroker" engine, except bored out to yield 3.4 L. The problem with ARI's method is that the cylinder wall thickness of the 2.8 block becomes marginal when bored that far. (GM 3.4 blocks are thicker castngs, from the beginning.) ARI claims that they test each block, to make sure the cylinder walls will remain thick enough once they are bored. Regardless, if their 3.4 ever needs a rebuild, there is absolutely no room to bore any larger. Once it's worn out, it's done.
With that said, I have never known anyone who had an ARI engine. There is, however, a 3.4 in one of our club's cars that was (IIRC) built in a similar fashion.
Is that true of the 87 and/or 88 blocks, too? I thought the oiling was fixed in the later engines. (Although, I'ts probably a crap shoot, which one you'd get.)
I have a Gen 2 3.1L shortblock I believe to be from a 90s Beretta, and it still has the Fiero-style twin oil galleries intersecting the lifters. The mains are fed the excess oil from the cam bearings.
I think it's hard to talk about the "oiling fix", as if there were only one update during 60°V6 production. Engines are often incrementally given upgrades... I think that as a general rule, one could conclude that the newer, the better.