When performance stops dead half way into a long ride thanks to not being able to get your foot (feet) warm and comfy, you run a strong risk of totally ruining the ride.
When you ‘only’ climb at 90% and don’t go quite as fast overall but are warm, content and comfy, thoughts of cleaning that tricky bit with SPDs will enter your mind.
Wonder which thought will stay with you the longest after the ride !
PS. Is it the foot position that causes the problem with SPDs, or the fact you don’t have the right shoes for the weather? I bought some goretex fur lined Scott SPD boots from Start cycles a couple of years ago. Keep my feet toastie in the most horrid of conditions and are plenty wide enough.
Think they were reduced from £200+ to around £90.