Oh a toughie and no simple answer unless your confident in what makes you happy
My personal experience was me waiting over 4 years for the RS not to mention countless hours and contribution to the community I have made with research, theories, and so forth. That wasn't enough for me to get one when a killer deal came up for the FiST basically a left over for 20K fully loaded. Money wasn't an issue though and it was more about time. I was tired of waiting and people who ordered when the banks opened still were waiting 10+ months later, my dealer I work at still didn't get theirs until after a year. This is why I bought a FiST instead of the RS that I could argue to myself with knowingly strong decisions and forgoing the years I put into research for the vehicle.
The strongest reason and kind of a new one for me around that time was my commute. I was getting extremely bored with my FoST on my 15 min stop and go heavy trafficked back road commute. My old job was even closer but there were roads I could open a bit on and actually get above 35, not to mention I could take the highway for one exit and keep it pinned the whole time lol.
I did as much research as I could for the FiST but basically came to the conclusion a Hybrid FiST could reach the same power to weight as a tuned RS. I wasn't expecting the FiST to be so damn good and I'm talking little things that I couldn't let go in the FoST, like horrid wheel hop (only cured with all 3 mounts), Impossible Heel & Toe ( FiST is better but not perfect) The horrid top end power with a tune (Again FiST is better but stil needs a turbo upgrade). As I drove the FiST my parts list that I originally made up off my experience with the FoST dwindled. The RS was my answer to the FoST and it's limitations, basically 10K+ to get the FoST to where I wanted on top of the 3K I put into it. I mean even the intercooler in the FiST does a way better job then the stocker in the FoST it's almost ok where the FoST was pure rubbish.
I only have 2k on mine so the real test will be when I slap a Hybrid on there and see how I like it then. I would say this though, if I still worked at my old job even though it was for Chevy lol, I would of waited longer for the RS. A light small vehicle suits my needs/wants better then a heavier version of the vehicle I had. So will I still get the RS, maybe but I'm building the FiST the way I planed first. I need to see how this platform is with aftermarket solutions before I jump ship, it is just worth it where the FoST wasn't.
I honestly think it's a fairly simple question with what I explained. They are different enough to come to a solid conclusion depending on the intention of use. I do not think you will have more fun in the RS just because it is a RS compared to a FiST and basically the solid solutions available to make it a very good vehicle. The RS does have faults, but you can make a wiked car for short money and 380whp for under 2K is easily doable. Things like the harsh ride though which I don't mind there is no amazing solution like MeisterR's as of yet.
The way I look at any purchase when it comes to vehicles is to have the ability to filter out the main goal. There are certain things the RS will have/do that a FiST won't and vise versa. Positives VS Negatives and to me driving impressions is the most important. In that case I don't think it's worth it and I have run a FiST in the back woods going 80+mph on dirt (another reason why I considered it). I don't think the RS brings a bigger smile in technical situations even on snow but the RS does have things the FiST will never have or do and you need to decide if those matter.