Road spacific shoes and wide platform cleats (like Look or Shimano SPD SL) provide more than a "roadie" look and light weight. The road shoes have a much stiffer sole and the wide cleats spread the point at which the pedal and cleat come together. It makes for a more solid feel like you are connected better to the bike. It also makes your stroke more efficiant.
I used SPD cleats and pedals on both MBT and road bikes for awhile and was glad when I went to spacific shoes/pedals as you are definatly making a compramise in either direction.
I currently use SPD on my MBT bike and for city riding as you can jump off the bike and walk easier in those shoes.
On my road bikes (commuter and road bike) I use SPD SL as I am not worried about walking in them (although once I walked three miles in them when I broke two spokes, it wasn't as bad as you might imagine). The road shoes and cleats just work better.
I always try and tell people that if you're worrying about "getting out" of cleats your worrying about the wrong thing, my experience is that "getting into" cleats has been more of an issue. With that in mind you'll find road cleats easier to deal with as clipping into SPD cleats/pedals is harder as they are tiny and since they are on the bottom of your foot (where you can't see where they are) it is sometimes hard to position them into the cleat.