we have a booster @ inlaws and had two different highchairs @ our house (quite nice chicco one at the moment and v cheap not great basic mothercare one previously), i found both the high chairs are better and much more convenient than the booster. not sure exactly what booster it is, just that its multicoloured plastic and folds up but it is a pita taking the tray in & out to put the child in it & not that sturdy/secure on the chair imo so wouldn't really recommend
I vote for a booster, we moved our DD into one at 12 months. They can sit at the table, which is more sociable and I find it easier to clean. I got this cheapo one from Tesco: direct.tesco.com/q/R.205-9082.aspx (it is often on half price special).
It has straps and a removable tray so you can use it like a highchair if you want and folds flat if you want to take it round someone's house. There are 3 height settings (our table is tall too, DH got it before he got me and I have to use a footstool!