The first thing you want to consider is the operator's past performance and node uptime.
Do they have a history of running high-uptime validators on other chains? What was their performance on the adversarial testnet (check
dashtec.xyz).
How invested are they in the success of the Aztec Network? The Sentinels from Discord, the Genesis Sequencers, Core Contributors of Aztec are highly aligned entities.
Have they correctly set the `coinbase` to the splits contracts of their past delegators? A little onchain sleuthing and you can find out how many blocks it took for them to set the right coinbase.
Also consider network decentralization. All else being equal, it is better to delegate to operators with less stake.