Yeah I second Vtech (or AT&T, also made by VTech) or if replaceable AAA batteries are important to you instead of settling for lower capacity shrink wrapped & plugged packs, I know some Panasonic models have those.
One thing in particular I insist on for the base unit is a call # numeric display. There was a time when that was getting to be a rarer feature but a few brands have brought it back.
Link to cell (bluetooth) feature is nice to have too.
Practically anything remotely modern is DECT6 except the cheapest of cheap models. It's definitely worth having for range and transmission clarity.
Try to avoid models with the numbers printed on the top of plastic keys. They will wear off, particularly if you sometimes need to answer with dirty hands or anyone has longer fingernails. Try to avoid models with silicone rubber keys unless you want to have to take it apart and clean the silicone oil off every few years as it comes out of the rubber and fouls the electrical contacts. Most have silicone rubber domes under the keys too but the less silicone there is, the lower the oil gunk rate.