Hi. Personally speaking, even though I have the trumpeter kit, I don't think a person could go wrong with either one of them. The really nice thing would be able to buy both of them and do the comaprison yourself. But if, and I really mean IF here, I can get just one done, I will consider myself extremely lucky and I know I will be totally burned out on ever building another one, at least of the K5s. Now a real nice 38 cm gun would be okay, or if they want to go for the ultimate, the 80 cm one, that would do too. Ha!
The Dragon does have fewer pieces than the Trumpeter kit, but these extras are mainly in the trucks (underneath), so the only person who is going to know is the builder themselves and others of us who seem to have gotten a good dose of the 'bigger is better' fever. And the Dragon, I believe, does give figures, where the Trumpter one does not., So you have to pick and chose. One thing though, I wouldn't pay over $100 for the Trumpeter kit. I got mine a couple months ago for $107+ tax here in the U.S. and that's plenty high enough.
Take care, sgirty