Better workout? Speed vs. climbing...

When cycling and looking to get better I don't know if I should concentrate or trying to run relatively flat areas along the coast (living in San Diego) or turn inland and climb some hills.  I know that "hill repeats" are the supposed Holy Grail of training but I'd much rather ride a loop.  Nice little loops and circuits generally don't have those good-for-your-legs hill repeats.  I really like seeing the results of climbing on my little Strava screen at the end of the ride and it looks like it burns more calories when I focus on climbing.  However, when I'm on the flats I get that nice high MPH average.  Once I get used to a good MPH average for rolling hills/flats (for me maybe 15-17 MPH) and I see the MPH results of climbing (dipping to 12-14 MPH) it's a little disappointing.

Can't Strava design some algorithm - other than a Suffer Score - to determine a good vs. bad workout relative to my personal ride history?  Maybe be able to differentiate casual rides vs. workouts vs. recovery rides?