I have a bike with an 8 speed internal geared hubs and it shifts very easily when stopped or moving, it has to be the easiest way to shift. However, downside is they add a lot of weight, three speeds are probably lighter, but if your has a lot of hills the 7 or 8 speeds will come in handy. My bike came with a Shimano and it wore out after 6 years (rainy and winter riding). Replaced with Sturmey Archer. If you go this route be careful with gear selection. When I switched hubs I also needed to switch chain rings to compensate.
Good luck!