No difference. A bluetooth speaker is a bluetooth speaker. Versions of bluetooth required may vary, but it can't be designated for one or the other. Now if it's not bluetooth and has a dock port, then yes, iphone only, etc are they use different charging/data jacks than android, but bluetooth, no. I could use a bluetooth transmitter to a receiver, a phone, tablet, iphone, my android TV box, my tv, to a bluetooth speaker, or in my case, bluetooth headphones. Or a PC with a bluetooth dongle or a laptop. Or your car.
It's just stupid marketing if companies are doing that.