The Manchester department is really good, and Tim Parkin is widely liked there, though there tends to be more emphasis on the Empire as opposed to the Republic, which is my personal opinion of course and I could be wrong, perhaps a look at this link may help
http://courses.humanities.manchester.ac.uk/undergraduate/modulelist.html?department=33I'm not too sure about Liverpool's department but what I will say is that they are far superior on Roman Archaeology than Manchester, and the last Roman Archaeologist at Manchester is retiring at the end of this Academic year, although he only teaches about Roman Archaeology in
Britannia. The Liverpool department also run a few excavations that deal with Roman Archaeology whilst Manchester do not. Dave woolliscroft at Liverpool runs the Roman Gask Project in Scotland, which looks at several Roman forts up there. I'm not sure if students of Ancient History at liverpool go onto excavations but I thought i'd mention this as I feel that study of the archaeology of the period concerned, as opposed to relying on literature can only be a plus, and the fact they hold such excavations may tickle your fancy (I myself have spoken to Dave about this as I really want to go onto that particular excavation)
The only thing I hate about Classics at Manchester is the fact that the little dinky room they have in the department is pretty puny in comparison to the other departmental libraries, for example the departmental library for Archaeology is awesome. The main library, John Rylands, is brilliant and is bigger than Liverpool's and holds more resources and materials, that said, the computers are ALWAYS taken by midday which is rather annoying.
I hope I've helped.