Just looked at the Mini Countryman and configured one as close as possible to the 500L that I've ordered. Was still missing half the technology and is £5k more.
What technology was missing? having done the same exercise I speced up your Fiat 500L at £20,390 with all the options I can find you've listed.
500L lounge twin air beats audio heated screen fancy paint 17" wheels I even added the comfort options as mini seats are infinitely adjustable (trying to even things up) I also compared the engines of the twin air and the 1.6 mini cooper (the spec I used to compare)
the thing that surprises me about the fiat website is the lack of data, specifications etc however a lease site gave all the information for an engine to engine comparison
so fiat twin air versus mini countryman cooper 1.6 petrol
Power
Fiat 105bhp
Mini 122bhp*
Torque
Fiat 145Nm
Mini 160Nm*
acceleration 0-62 (s)
Fiat 12.8
Mini 10.5*
Top speed
Fiat 112mph
Mini 118mph*
Fuel Economy Combined (mpg)
Fiat 58.9*
Mini 47.1
CO2 emissions g/km
Fiat 112*
Mini 140
VED band and annual Cost
Fiat (C) £30*
Mini (E) £120
unladened weight
Fiat 1260kg
Mini 1265kg (only 5kg in it)
So the mini is more powerful faster etc the fiat is better on economy and cost, but take into account the use of a turbo in the fiat which the countryman cooper doesn't have (just a point of note) and the 1.4 fiat engine doesn't fair so well against the 1.6 mini
so to get all the spec of the £20,390 fiat in a mini it cost me £22,190 on their online Configurator just adding all the options the fiat has as standard and the options you've selected (upgraded stereo package heated screen wheels and fancy paint choice. floor mats, glass sunroof etc) basically matching the mini to the specs of the fiat and the total price difference is £1800
which I don't think is too bad £1800 can be easily lost in the difference between finance packages on the fiat or on the mini and I know mini have a big push on cheap finance at the moment. and I am certain £1800 worth of build quality can be found in the mini above the fiat (although the fiat is very good)
The Mini has a huge number of additional options that just aren't available on the fiat, not big things just lots of little customisation type stuff being new the fiat 500L don't have anywhere near as many options as fiat like to imply, infact the 500 doesn't have anywhere near the options of a countryman
as for the fiat being bigger?
Boot space comparison
minimum
Fiat 343ltrs
mini 350ltrs*
expanded
Fiat 400ltrs
Mini 442ltrs*
with seats down
Fiat 1310ltrs*
Mini 1170Ltrs
so the fiat is only bigger boot space wise with the seats folded down and neither I would say scrimp on rear passenger leg room, obviously the fiat gains somewhere but carrying tots about as per the target market, the higher capacity is needed with the seats up in addition the mini has roof rails if you need to lash down anything sizeable
I'm not criticising your choice of car if a cheap to run family car with a quirky look is what you want then the fiat is the obvious choice out of the two as the Mini is more expensive to buy and run
A more style conscious, keep up with the joneses type person would opt for the mini badge and reputation for build quality better performance and with greater adaptability and customisation yeah so it costs a bit more but they want the joneses to know they can afford more, even if it is only £1800
One thing that can be said for the mini is people are interested in it when I had a Saab people would ask 'how's the saab' the same applied to the Rangerover I owned and again with our mini cooper hatch back people ask 'how is the mini' with all the fiats i've owned no one has ever asked 'how's the fiat'
Plus you can do this in the Mini (if you are completely mental)
https://www.youtube.com/watch?v=4u0jd5bDw4o
or this
https://www.youtube.com/watch?v=8wgIrt6VtLg