I inline skate on Seba Igors (freestyle slalom skates) with a rockered frame so probably a similar profile to a hockey blade on ice. Yes, I think price matters for inlines as on ice - you need the right support - and obviously fit. The rockered setup is less stable than flat but easier to turn with and do tricks. I think if you just want to stride along then flat setup is fine, but I do a hybrid of slalom, figure, dance, hockey and rink rat skating on my inlines, rockered setup is better for that. You can achieve it without a rockered frame by having wheels of different sizes - my setup is probably 78-80-80-78 though once the toe and heel wheel get worn it's more like 76-80-80-76.
I like being outdoors in the fresh air, being able to skate clockwise when I want, and listen to my own music.
I think all types of skating cross over and complement one another. I skate on figures on ice, so the blade is quite different and the boots (no real heel on my inlines so you need to pitch yourself forward, even more knee/ankle bend, to be properly over your skates. It took me a few months of switching between ice and wheel to get used to it, now it is second nature. My younger daughter and a chum of mine both switch and are pretty accomplished at both. You adapt your style and the moves and tricks you do to the way the equipment and terrain works - some things (the basics) are pretty much identical, others (spinning, stopping) are quite different.
For anyone that has not tried it's worth a go, and be patient - when you start out and hit the odd bump which you do not find in a rink you'll wonder how or why anyone skates outdoors, but when you learn to stay loose and down in the knee and ride the bumps, scissor over them, you'll learn to love it.
I don't street skate, but some do. There are organised mass skates every Friday and Sunday in London (LFNS and Sunday Stroll), with music on the move.
I do lesson with Asha from Skatefresh who comes from a quad figure background. There's a healthy slalom and dance scene in Hyde Park, always someone happy to show you their moves and share.
Asphalt hurts - wear wrist guards if you don't want grit embedded in your palms. I wear a helmet these days - you don't slide on concrete, and it makes me a bit more confident and relaxed.