The blockchains we're discussing here are about uniform replication & inter-node agreement, so constant performance is as the system scales is the goal. Our implementation of ScalableBFT runs at 8k-12k transactions per second, not 5-15 tps, and it maintains this performance as cluster size increases (up to some limit, we haven't managed to test it past the limit yet and think it's around 5k-15k nodes).

The other deterministic BFT systems like PBFT and SmartBFT are a little bit faster for small cluster sizes but slow down for every added node, encountering full system locks before 256 nodes. It's worth noting that these systems generally do not do pubkey sig verification on every command, instead relying on consensus and direct replication via TLS for authorship guarantees. The drawback, of course, is that an attacker is one server (the client's TLS server) away from inputting fake commands that the system deems real + smart contract authority is handled logically and not cryptographically... we see the CEO and the Mail Clerk having different keys to be a huge benefit from a Bitcoin-like approach.

This makes the bottleneck for us crypto-verification. Verifying 8k-12k signatures per seconds is pretty tricky if you don't skimp out on the crypto, which a lot of vendors are doing in the name of speed.