Witchipedia

As a Hellenic practitioner of 20+ years, I find traditional Greek and Roman practices to be very different, in terms of look and feel. Greek ritual is like poetry; Roman ritual is more like a contract negotiation. >8) And being a strict polytheist, I'd consider them to be different deities; just because Roman writers co-opted the Greek myths and put Roman names on them doesn't make them the same, IMO.

That said, if you're not aiming for traditionalism or reconstructionism in your practice, go with the ones you feel more comfortable working with.

I agree that the Greek and Roman pantheons are quite different when you really get to know them. Venus, for example, is much more of an agricultural Goddess related to viticulture, and Aphrodite is closer to the sea. It was the way of ancient honor societies to impose their culture on others, but the history remains. That being said, it's not that hard to incorporate the planetary energies into a Hellenic practice. I am not terribly traditional about it, but I have found that using the zodiac signs works very well. I have incorporated them into my Noumenia observations, assigning each Zodiac sign to a God or pair of Gods, so that each New Moon, someone gets a ritual and it cycles through. The New Moon is in the same zodiac sign as the sun. I once came across a calendar that was attributed to Orpheus (I can't say how accurately) that didn't quite match up with mine, though it was close. I just looked for it again but I can't find it. I think Hellonion also runs on a similar model, but I don't think they adhere strictly to the New Moon because it's just too complicated when there are a lot of people involved and the modern calendar cares nothing for the lunar cycle. I am rambling, I am not sure if I was helpful.

With regard to the issue of different pantheons in general, I don't think it's necessary that you restrict yourself hard and fast to one pantheon. I do think it's important to establish a relationship with your Gods and not call every God of Love ever conceived of to come help you out with your marital problems, but rather the one that you know and who knows you and might actually care based on an already established relationship. As a hard polytheist, I don't believe they are the same Gods, obviously, but since I do believe that all Gods are individual and real and true and valid, I think they're all due at least the basic level of respect you'd give a stranger of some authority. I have been to a festival or Pomona, and a Wiccan Circle, and various other groups that had their own Gods and I give them full honors when I am there. When I find myself in a Christian church, I do that God honor too, just because it's polite. When you go to someone else's house, you are nice to their friends (and their Gods). I also have connected local and perhaps unnamed (at least in human terms, officially) Gods or Daimons that honor, because I am on their land, after all.