I tried Specter Desktop briefly, but prefer Sparrow, mainly because of Electrum server support.

If you only every use either with brand new wallets, then I suspect they’re similarly fast. The difference is when you’re recovering.

I haven’t kept up with Specter development, but when I tried it, it connected directly to your Bitcoin core node. It didn’t support connecting to Electrum server. So that meant that recovering a wallet meant having to scan the block chain, which could take several minutes or longer, depending on the CPU and hard disk speed of the Bitcoin node.

If you use Sparrow with an Electrum server backend, recovery is significantly faster because it uses the Electrum server’s index rather than scanning the Bitcoin core historical data block-by-block.

Now, if Specter has implemented Electrum server connection support, my point is moot. But in any case, recovery speed was a big part of my reason for picking Sparrow.