I'd say something like this:

1. Lnserver (cheaper fees) or Olympus (fairly high fees)

2. LQwD (fairly low fees)

3. Flashsats (mid-range fees)

just based on liquidity flexibility, in other words, their ability to respond to demands on their liquidity. For the most part, small transactions like zaps are likely to go through without trouble on any of these lsps.