I know they use more energy but I find using my hamstrings and my calfs not just my quads helps me climb on the road bike.
Not everyone will get on with it. But I definatley noticed my quads being less stressed. And my leg working as a whole unit.
(Also improving core fitness helps anyway.)
Pulling the pedals up quicker allows me to spin like I never could before.
Also I find going downhill at high speed over bumps in the road-well being clipped in keeps me on the bike-part of the bike instead of holding on and bouncing on the saddle.
It's up to you whatever you use and what works for you.
I have loads of traffic as well and I would only use spds. Country lanes and I love using the large platform road pedals. But only as I can't get out of the lowest setting!
Try double sided mtb Spds -practice in the lounge and you'll realise after a few turns you can clip out of them really easy! And after a few goes you'll be fine.
If you really don't want to then don't force yourself.
Or ask a pal to show you how easy it is.