I agree with getting platforms and trying them. Try going up the hill in question. If you can't make it, then you know the clipping in was giving you something... and if you can, then you win!
To be honest I really think the main thing is being comfortable on your bike. You've tried the clipless for long enough now that you can say you gave it a fair try. Do you have platforms on your commuter you can switch over to the road bike for trying?
Personally I haven't tried clipless and I don't plan to. I like platforms. Both bikes I bought came with clipless and I asked them at the store to switch them to platform before taking possession.