I echo the comments - I test drove the R recently - not with the intention of buying but just so I could have an informed decision when I get told either of these two things
1. You should have bought the Golf R
2. The Golf R is "faster"
The R may well be faster off the line but a sorted GTi (PP) with decent tyres won't be far behind and on the run it's lighter weight does tell. My stage 1 PP has left many an R driver wondering why they are carrying around a heavy 4WD system, paying much more insurance and undoubtedly a little more per month on the PCP.
Most importantly - I've never wanted an R - the GTi was on the car bucket list - box ticked.
Much more insurance? My R costs less to insure than my old GTD and only £12 more than our Polo GTI+, and I've been maxed out on no claims for 12 years, and haven't passed any significant age milestones to reduce my risk recently. I'd imagine a declared remap on a GTI will cost more to insure than a stock R. Of course you can remap an R and open the performance gap right up again.
The R costs very little more on PCP due to higher cost being offset with markedly better residuals. The R used to be significantly cheaper than a GTI on PCP when it had the sky high GFV. Back then in late 2014, between the £18500/3 year GFV and the dirt cheap leases, no one was buying a GTI.
So with those 2 factors out of the way, it's a matter of preference.
The current Polo GTI drives very much like a Golf GTI it's only about 40Kg lighter, but feels very sharp in handling like the Golf, when compared to the R. Completely different character to the R - which is like an unflappable tank with a lot more at the top end than either of the GTIs, and that obvious 4WD standing start traction.
With all that though, by the time you've wound either GTI up to the red line in 3rd you'll be under the scrutiny of the speed cameras even on the motorway.
I've had my R far longer than any other VW bought from new (I'm on my 9th). The biggest spoiler for me is the absolutely sh!te tractor/JCB grade manual gearbox.
It's definitely more fun to drive if you have the opportunity to wind it right up, it's quick enough to not feel a bit dead due to linear power delivery that all post 2012 VW models seem to suffer from. I suppose the remap does the same thing.
I find the Polo GTI+ as fun to drive, but in a different way - agility vs the R's raw power delivered in a hugely composed way.
Truth be told, by the time you get over the fact you've lost about 0.8s to the 4WD, there's not much difference to the rest of it for the Golf or Polo GTI. 30-100mph will be significant. All that power and only legally being able to use a fraction of it every day.