Like the majority of people I voted for "mostly
Roman with a few other ancients".
One reason of course is that
Roman coins of virtually all
types and varieties are readily available and, at least in low grades, very affordable. Probably the biggest reason for me is that identifying and attributing the coins, and finding out the
history behind the people and places that issued them, as well as the
history of the monetary system and coins themselves, is much easier with
Roman coins - due to the huge amount of reference material (both printed and online) available on the subject, and the fact that most coins have the portait of the emperor/empress and a readable Latin
legend.
Greek and other
ancient coins, however, I've found very difficult to identify; with most coins it's hard to even know where to start looking.
Roman provincials can be tricky enough, and these at least usually have legends and emperor
portraits on them!
Another major reason is that, as I live in
Britain,
Roman coins have much more local historical relevance - I live not too far from both Silchester and St. Albans, both of which have
Roman city sites + many finds on display in local museums. I've even found a couple of
Roman coins myself (both late bronzes in very
poor condition) with a metal detector. On the other hand, I know very little about most of the states and kingdoms that issued
Greek coins, and am not sure where to start finding out!
My other main coin collecting area/focus is British hammered (17th century and earlier) coins. However, these don't really count as "ancients" other than the handful of
Celtic coins (mostly Durotriges bronzes and silver quarter-units) in my
collection.