Let me know if my criteria are sound, or if you have any concerns. I'd like to get started as soon as possible.
Unless I hear otherwise, I'm going to start reaching out to the clients that meet my criteria for this research.
If you sent the first option out in an email, you might be waiting a few days to get the go-ahead. The second option, and you can begin immediately.
The difference is night and day.
I first heard of this phrase through this lovely one-page website unlessiheardifferently.com, and I use it all the time, and have gotten nothing but positive feedback.
Give it a whirl yourself, next time you want to get something rolling and don't want to wait for the explicit permission of those around you. They'll thank you for it.