For our shop, we purchased all cordless Milwaukee M18 tools for drills and impacts. For us, it allowed us to standardize on one battery which made things very easy. I have lots of experience with Milwaukee tools and they have shown themselves to be high quality with very few issues, and they have been great when any problem arrived.
As a side note, I was in you exact position at the beginning of this season. Here is a link to a Google Sheet with all the tools we purchased, with links, prices, etc.
https://goo.gl/qYTa66
Also, feel free to PM me, I would be more than happy to talk to you about my experience starting our shop and any questions you have.
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2017:
Team 5940 (Silicon Valley Regional/San Francisco Regional)
2016:
Team 5940 (Silicon Valley Regional Rookie All-Star and Quarterfinalist, Curie Quarterfinalist)
Volunteer: 2016 (Chezy Champs Field Reset, Capital City Classic FTA, MadTown ThrowDown FTA)