I'm not 100% sure I agree completely with the points raised (given the exclusion of the wallyworld type coilover "shocks"), as full (front & rear) suspension isn't always for comfort alone, with today's adjustable dampener shocks fully suspended bikes can even gain stability over unsuspended in certain conditions, such as washboard & other repetitive road variances, let alone recovery from major impacts, bumps or holes...
For smooth, high speed & competitive track/pavement use there's something to be said for running a hardtail, or even w/o front shocks for that matter - but I think it's more simplicity & weight savings than anything else, dialing in the shocks for a firm, quick response (bound & rebound) negates much if not all the "squishy" feel. As for "energy to be lost through suspension" I
think that's primarily applicable to pedal power as the shock's compression rate would have little to no effect on the power transfer from engine chain to rear sprocket... even if it did (depends on suspension geometry, compression under engine load), it couldn't be much, negligible even in comparison to say, the flutter drag between two different T shirts...
Personal preference & riding technique on the other hand - those I think are far more direct factors & ones not to be underestimated.
Were I to build a dedicated track racer, it would most likely be at least a hardtail w/only moderately wide tires - but this would be for weight & rolling resistance reduction, anything I build for the street will have at least front shocks as no minute preformance difference is worth the pounding & numb hands lol