The Humber is heavier, less efficient and lively and FEELS more seaworthy, the Leeway is lighter, livelier and with less freeboard etc is less where you'd want to be caught out in 30k and the associated sea.
I have the original Leeway no. 1 with an Evinrude 115 on it and it's been fantastic. It's incredibly economical (averaged 10l/hour over the course of it's two and half years with me, mixed use, commuting, skiing, wakeboarding etc). The build quality is second to none, the rigging was ok but we have changed one or two things for the better and it's as quick as hell.
It's also coped very well with everything we've thrown at it including going out to the inshore Volvo Ocean Race leg at Portsmouth in 40k and horrible seas. But it has to be said that it takes more thought and effort to drive it in that sort of stuff than it would a Ribcraft/Humber etc. Horses for courses really.
Probably your best bet is to be honest with yourself about what you are really going to use it for and the conditions you will use it in and then the decision should be easier. Sub 20k winds/associated chop etc then it's the Leeway, above and it's the Humber.