It's not as simple. Some networks use other hashing methods, so just comparing hash to hash is pointless - if anything, you could compare instructions per seco

It's not as simple. Some networks use other hashing methods, so just comparing hash to hash is pointless - if anything, you could compare instructions per second, not hashes per second. Then, for certain hash methods, GPUs/FPGAs/ASICS give no speedup, so even if there are far fever instructions per second, they would be just as expensive to attack. Also, there are POS/DPOS, and other proof of sth networks, where it's not really about hashes, but about other resources - again, cost of attack would be a better metric here, not hashes. But most importantly - after a certain point, a network attack is so unlikely that additional security matters much less than other system properties, like speed, ability to execute smart contracts efficiently, or the ecosystem of startups around it.