Key with any battery powered tool is that you are buying into the platform, not just one tool. Batteries are at least half the cost of the tool. So, if I was already 'invested' in one battery platform, I would start there.
Not an issue, and money is no object? I would check out the Husqvarna T540ixp, with a couple of their top end batteries. Has a good reputation for a pro-level battery saw. Husky has some less expensive models too.
STIHL if you like STIHL products or have a dealer relationship.
Makita has 2 versions: XCUo9Z, 36volt (2 - 18 V batteries) and XCU06Z, 18volt (1 - 18 V battery) that are very compact. I would choose the 36V for more power, or the 18V for lighter weight. A plus if you already own Makita 18V contractor tools.
Philbert