Its the same chassis - check out the dents carefully..... the body colour differences depend on the camera light filter ...... but I see what you mean by the different camera positions over different action days.
All those suspension mods (courtesy of Abarth & Co et al on the 500) really do the job. It just shows that the 126 with all the 500 mods makes a great little toy..... and its bomb proof so long as you don't use tyres with too much grip/ on too dry a surface.
..... With no weight in the rear and such a short wheelbase .... add some driver skills revs and hey presto!
Well you can take the engine and box out on your own - usually with jack - but its a one man lift too.... so there isn't a lot of weight anywhere in the car. What I am referring to is that the pendulum effect is almost absent.... when hanging the back end out, the time it takes to respond to opposite lock is quite small.... which is confidence inspiring for the novice et al. (So there's little more weight in the back relative to the rest of the car and its track.
This then gives more opportunity to keep the front to rear balanced with a load of throttle - and generations of Italian motorsports pilots/ engineers have added a load of tricks to stiffen the front suspension against bad movement/ habits. For sprinting you are looking for slide - oversteer action. The only times I've ever seen this upset is when high grip surfaces and tyres overwhelm the original setups - then they all roll quite easily.
But if you were making a Fiat Bucket List - sports Fiats you've really got to give a real go before you hang the gloves up ...... then I'd thoroughly recommend the 126 with Abarth setup..... as the 126 is really a mark4 Fiat 500.... and it comes with lots of stronger bits as standard.