I think the one thing that struck me with Perth was that it was so far from anywhere else in Aus. It really is remote. Yes there are towns along the coast, but there are no other major cities or even really large towns that I could see as appealing. Its a trek to anywhere else. Adelaide has the benefit of being more central and not so far for flights to Melbourne and Sydney etc. Adelaide and the surrounding area felt more populated along the coast, more connnected for that reason.
I think the climate thing is becoming a bone of contention amongst some here :p TBH Adelaide usually has a great summer climate but this year has been a bit off. Also spring and autumn have been pretty good there when I've been there. Its not like its an awful climate and like the UK summers or winters usually. Lets be honest, the UK hasn't really gotten over 25C for more than a few days at a time in the past few years. My hubby, an Aussie from Adelaide says that UK summers are like Adelaide springs and he can live with that. He isn't looking forward to moving back and facing the 40C plus temps that can be reached. The heat is the one thing he hasn't missed living here in the UK