I would say skip over the 12 volt systems for a first tool. Unless you live in a very small space or only going to do small jobs etc. Reasoning - there are some compact 20/18 volt system stuff out there - that have more overall power. So for a First cordless drill - I would start with the smaller drill/driver offerings of the 20/18 Volt families. Dewalt, Milwaukee, Makita, . . . . . . .
meh - pick your flavor - that fits your hands right. I say it like I tell people looking to buy their first hand gun. there is more out there than a Glock, or Sig or . . . . . . We are all slightly different. I prefer Dewalt stuff as their stuff works very well and happens to fit my hands gloves or no gloves wonderfully. So I bought into that system.
I also like that they are an American Hq company and traded on the New York Stock exchange - but that's a political aside.
I find nothing wrong with the Milwaukee, Makita, or Bosch devices.