These do vary a lot from mint to mint but I find the Rome ones by far the worst in artistry, craftsmanship and even size and weight! Although very similar style wise to Ostia and perhaps little less to Ticimum I much prefer these later two mints: All the above are Ticinum. PTDot with Star (RIC VII 16), TT Cross and Star (RIC VII 45), ST P (RIC VII 68). Both Ostia and Ticinum produced small coins like Rome but they were always better centered and struck. The Cross is thought to symbolize Christ and the Star the Emperor - interesting if true but nobody knows for sure.
Trier seems on the whole to have produced the most substantial and 'well made' coins and also had the most 'efficient' mintmark and fieldmark system (typical Germans!). A large (5.3g) Trier coin next to a smaller (3.1g) Rome 'T in Wreath' example'. I also have a couple of Half-follis coins from Trier, the only mint to produce them (shown with the above follis): The follis is RIC VI 875 and I think the two halves are RIC VI 899? I agree with Martin that the Lyon coins are OK and along with the London ones show the most character, the Lyon reverses have attributes not of the other mints show.
My favourite Sols: Siscia seems the hardest to find - I do have one but like the Royal family it doesn't like having its picture taken so I wont bother trying to post it. A Trier example showing what looks to be full silvering below the green - again hard to photo unfortunately. An Aquileia and a Rome example show Sol 'with captive' at feet. Pair of cuff-links picked up on 'the bay' for about £10, ad stated 'fake Roman coins', I thought they looked real and they were, excellent quality Ticinum and Arles coins :smile
The Ticinum reverse (right) is just as nice as the obverse, its a PDotT with a Star in left field. The other one I mis-attributed above, its actually Lyon and its reverse does have a big scratch on it unfortunately. I think they must have been in these mounts for quite some time judging by the amount of 'gunk' that I had to clean out to ID them. No pictures of the reverse unfortunately but I did find out I got them from a UK seller for £8.86 :smile