So this is what I would recommend:
If you want to just stuff an engine in and leave it alone without modding anything inside: B18C (more power stock)
If you want to stuff an engine in and rebuild it all motor but not go too crazy: B20/VTEC (great power with pistons/rods and mild cams)
If you're going to go all out and spend a ton of money on the block, get the B18C. You'll have the girdle from the factory, oil squirters if you stick with the stock bore or get pistons that are notched for them at higher bores, VTEC set up from the factory... and if you resleeve, you'll have the same bore options as the B20.
My first block was a B20 with a B16 head, and it made awesome power. The next two I built were based on the B18C, but with the longer stroke crank. They displaced more than the B20/VTEC setup and made more torque too- but the block had a nice Golden Eagle sleeve in it to bump the bore out way beyond what would be considered to be safe on a stock B20 sleeve.
By the way, the rod/stroke ratio on the B18A/B and B20 is 1.54:1, the B18C is only 1.58:1. It's not significantly better. You can spin the B20 bottom end out to 8000-9000 if you have your parts chosen correctly. It's not a big deal. Now, all the engines I have in the current cars (and truck) are 1.8:1+, so I can have LOADS of fun.