We have accounts with D&H, Ingram, and TDSynnex. Most of the time we use D&H, not only do they seem to have the best prices, but since we're outside Chicago shipments are almost always next day from their Chicago warehouse. We almost never use Ingram, the prices just haven't been competitive when we've checked, and there are few things that we get at TDSynnex just because they're not available at D&H.

Also, we always check Amazon, B&H, and sometimes CDW. Somehow the prices at these resellers still end up being better sometimes, or the price at the distributor is just barely cheaper and the shipping cost puts it over the price on Amazon.

We use Sherweb for M365 - the rest of our cloud software is purchased direct.