If, by adjustable dumbbells, you mean stuff like the PowerBlock/Bowflex types, don't waste your money. They're far too expensive for the weight range... aside from any "personal" preference as to how convenient you find them, only a few brands (like PowerBlock and IronMaster) are any good and they cost way too much to justify not just buying some plates, collars and bars.
... but if you really want to buy them, PB and IM are the way to go.