I have the Specialized Tahoe mountain bike shoes and Pearl Izumi mountain bike shoes with SPD's on my road bike. I find them to be very comfortable. As an added bonus is I get to use the shoes in spin class too as most spin bikes use SPD pedals

Does your shop have a return policy?

I don' think anyone can tell you what's best. I love SPD's but I'm sure 100's of other people will tell you they love their frogs or their eggbeaters. I was lucky enough to pick SPD's and they just worked for me. If they hadn't, I would have switched them out until I found something that worked. I say make a choice (Do a search on the forums and on the web for all the pedals you are considering) , and most importantly try them out and if they don't work for you, you can always switch them out later. If the bike shop won't take them back, you can sell them here, on craigslist or on ebay. Good Luck with whatever you decide.