Wake from suspend-to-RAM (and likely with a radio power up) is going to be gobs more expensive than a wake from retention because you're both coming from a much

Wake from suspend-to-RAM (and likely with a radio power up) is going to be gobs more expensive than a wake from retention because you're both coming from a much lower power state (you were doing great before and now you're not, so a big change in energy usage over baseline) and it has a high overhead (the core cluster/SoC has to go through power on reset and get reconfigured by SW). This greatly contrasts with a wake from WFI where at minimum all architectural state is retained but generally caches and predictors are retained for quite a while.