For Dragon 747, I would see them as old but solid models that are a bang for the buck should prices are ok. They ain't spectacular and perfect, but are totally decent enough to be a good option on 747s.
1) Accurate fuselage shape
Fuselage shape on Dragon 747 is never a problem - in fact the nose shape is still regarded as the better ones when compared to newer moulds such as the Phoenix one (Which is rubbish) or even the new JC ones (Which are decent)
2) One of the two B744 that features all engine options
Unlike the old GJ/BB and even Phoenix that use a mixture of CF6-80 and PW4000 for the two engine types, Dragon is the first manufacturer that produce proper PW4000 for their 744 - a feature that only JC's new 744 mould also has. If you are really going for utmost accuracy on engines, then Dragon is a definite plus. (P.s. Some late BB's are widely believed to be using CF6-50s to pretend as CF6-80s as the casting for CF6-80 are believed to be destroyed)
3) Discreet Wing seam
It has a seam for fitting the wing cradle - but it was located at the bottom of the model and is very small - which makes them looks like a slot-in one when viewed from uptop - An angle that we mostly see our models. Only when you look at the bottom will you realise the presence of the seam.
4) Detailed Control surface
By utilising plastics on wings and stabilizers, Dragon could make deeper grooves on these components for a more detailed look - and they indeed look gorgeous!
1) Plastic wing and stabilizers
It really is just a matter of preference - The lightweight of plastic allows Dragon to create deeper grooves hence more detailed control surface - but in turn it creates the problem of color change - I have plenty Dragon 747s have their colors on the plastic components covered with a layer of yellowish tone - you might want to have a look on the status of individual models at situation may vary from model to model.
2) Simple landing gears
It is another major painpoint for Dragons in general - but you might still want to have a look at how simple they were compared to their competitors.
3) (744) Wingtip size ain't right
I didn't realise that until recently when I compare my 744s - the Wingtip fence on Dragon 744s seems to be a tad smaller than her competitors and did not reach the full width of the wing - a bit annoying once you notice it - but otherwise still ok as they ain't too small to be annoying.
4) Nose shape inconsistent
The nose shape of Dragons are tend to be hit or miss to me - some in my collection have really sharp nose while some are much rounder - you might want to check the nose shape one by one to confirm the status of the ones you'd like to purchase.