Murph, please take this as respectful disagreement, but I wouldn't be so fast to compliment to the Trumpeter kit. I'm in the midst of building the floatplane version after exhaustive research, but have had to put it on hold yet again while still MORE correction resin parts are cast for it. It is a collection of one inaccuracy after another. And that's forgetting the stuff specific to the floatplane. Just the parts specific to the Spit Vb, which is pretty much everything but the gear being replaced by floats and some modification to the rear fuselage. The kit has the wrong canopy (try fixing that one in 1/24) for the type as well as the wrong windscreen, the wrong prop blades, a seat that doesn't seem to go with any aircraft of the period, let alone a Spitfire. The horizontal stabilizors, which were, of course, sheet metal, are molded in an exaggerated fabric covering (!). The big spade control column comes about up to the pilot's face, the cannon are wrong, though usable, and there is the absence of the cannon firing switch on the spade grip (it's pretty conspicuous in that scale). There's an enormous "step" all the way around the rear fuselage that is virtually impossible to fix without using the resin correction parts.
And the cockpit detail on this 1/24 kit is no better than any good 1/48 scale kit. In many cases it is just downright incorrect, such as the shape of the throttle quadrant and the gear quadrant, also poorly shaped and, though this is getting too picky maybe, the lever is in the gear-up position (this part is not used, obviously, on the float plane, though Trumpeter would have you install it according to the instructions). The framing over the engine is mythical, BTW.
I could go on, but you get the picture. Airfix, in fact, has upgraded their Spit I, though I can't vouch for the newer one being better than the original, having only read reviews saying it is.
There are so many errors with both Trumpeter versions of the Spit Vb that MDC has a whole range of resin correction parts, large and small, for both the land plane and the floatplane versions. It's like I've been going on and on about: Trumpeter has a lot of nerve putting a suggested retail price of 120 bucks on a kit that has flaws that even a casual Spitfire buff would not have made..
So before investing in either the Airfix or the Trumpeter kit, read all the reviews you can find. I've seen a couple of people on the web, who apparently have plenty of disposable income, who bought both kits and combined the correct parts from both to make one accurate Spitfire. But if you are hellbent on making a big Spitfire, the surface detail on the Trumpeter kit is nice and if you can afford to buy all the correction resin, or if you are willing to overlook all the errors, go for it.
I wouldn't go on like some overwrought rivet counter if this wasn't a kit that cost so much, but people deserve better for their money. And I'll never stop shouting that mantra. It's not like the guy down at the LHS is going to let you go through the parts and compare them to a Spitfire reference book before you buy, and the problem with mail order is obvious. I suggest finding a review column in a web site or magazine whose word you trust, and pay attention to what they say before investing. That's not the perfect solution, but it's the best I can think of.
TOM