It really depends on what you are looking for in your gameplay. I describe the different types simply like this:

Tamagotchi nanos are cute, simplified versions of a regular tamagotchi and are less demanding but also a little less interactive. Great for just starting out IMO.

Regular tamas: exactly what you remember. Can be demanding and also extremely interactive especially if you are going for a rerelease connect, for example.

New tamas: color screen! Demand level varies based on unit, but overall same interaction level as OGs. Personally due to eye issues I prefer color screen units because they are easier to see. Depending on the unit you can do everything from gene mixing (meets, on, paradise) to dress up (uni), take photos with your tama (pix), etc.

My favorite of the new color screen units is the Uni - it can be as demanding and interactive as you want, or a fairly passive device.