Nah, the 1.8 is more stout. It was originally developed to go in the 323GTR which was turbocharged, so the BP motor (1.8L) is stronger. The 1.6L B6 ain't a bad engine though!
If you're looking at an early Miata, keep an eye out for the short nose crank issue.
https://www.miata.net/garage/crankshaft.html