Hi Mocha,
I've used both, and sometimes I use both at the same time for no particular reason other than I am a moisture freak.
As for hold with the Gel, that is not it's purpose, it's simply to moisturize, activate the curl pattern, and condition the hair. Now, it *may* provide hold for some but I haven't found that to be the case which makes sense as that's not really what it's for. Just an FYI in case you buy it expecting it to do something different than the jar says it will do. I know I hate when I've purchased something because I expect something totally different then it does something else, so I'm just lookin' out for ya /images/graemlins/wink.gif
I personally enjoy the gel but simply for "ease of application" , I mean it doesn't run /images/graemlins/grin.gif /images/graemlins/grin.gif So it's easier to apply like to braids etc. and you don't have to worry about "drip". The spray works great to moisturize the hair as well, and for me is as moisturizing as the gel.
Now for the activator, I think some of the girls if they want hold will use another "styling" gel, just a little bit, over their curl activator to tame edges.
Also in my experience it does help with bringing out curl definition, but I'll mix it with Glass or another holding type gel to lock the curls in.