Where's Covenanter? Maybe it was personal...
Positioning aside, it all comes down to how well the speaker has been designed and built, rather than whether it is a standmount or floorstander. Sure, a floorstander will have an advantage with regards to cabinet volume (presuming same size and number of drivers) and therefore bass extension, but insufficiently designed, a well designed standmount could well outperform it in almost every way - possibly even bass extension!
A previous post mentioned not considering floorstanders under the £2k mark. I would say that is slightly excessive (personal preference etc), but I agree to a point - I'd be considering more expensive floorstanders to compete with cheaper standmounts. Under £2,000 there is a handful of floorstanders I'd purchase for my own use - but many more standmounts. When you have standmount speakers like Sonus Faber's Toy, KEF's LS50, Q Acoustics' Concept 20, ATC's SCM7 and the like, you have to then be looking at least the £1,500/2,000 mark to find a competing floorstander. By "competing", I mean retaining the treble and midrange characteristics whilst providing better bass extension.
That's not to say of course that any £1,000 standmount is going to beat a £2,000 floorstander, or even some £1,500 ones - it just comes back to how well they've been designed/built. Then again, those that prefer more bass quantity or presence will more than likely prefer a bigger floorstander for their money than an equivalently priced, leaner sounding standmount, regardless as to whether the standmount might be technically superior. They can differ enough to generalise that one person might prefer one type over the other.