I can only comment on the Airfix one. The shape is supposed to be good & the ones that I have built haven't needed a lot of filler. I have never been able to get the removable cowling panels to stay in place so have always glued them down. The biggest downers with the kit are the lack of boxed in wheel wells & the very basic cockpit.
The side wall detail stops towards the bottom & instead of having a fuselage side that should continue curving round it just opens up into a void for the wing root. Have a google for a build review & you will see what I mean about the cockpit. The detail that is there isn't up to modern standards. The kit is over 40 years old in its defence though.
I haven't seen any PE for the Airfix Spitfire. The only additions that I have seen are a film instrument panel & a resin control column & throttle quadrant. (all on ebay). RAF seat belts are available in 1/24th as are brass Browning's if you choose to open the gun access panels.
I have seen some spectacular builds of the Airfix kit as it makes a great canvass to detail.