I like the whistles saddle bag best. Looks the most classy out of the three and I think it's a fairly classic style too. I think chain bags work better for evening.
Personally, and this might be controversial, but Mulberry to me is a bit obvious, unimaginative, and "default designer bag". Some are nicely made, simple designs but generally i find them all a bit meh. And for £££ i want more than meh!