Hoping for guidance on where to find info. We're (3 couples with varying experience)toying with a 1 way 9 day charter between Antigua and St. Martin in early Dec 2015.

I realize this is the BVI forum but with the wealth of experience here I'm hoping you can point us toward where we can do some research on:
Pros and cons
Charter companies that will do this
direction at that time of year
possible itinerary
clearing in info
Great places to explore
anything we might be missing
Thanks in advance for any guidance.

I would start by calling a few SXM charter companies and see if they even would allow this. I would assume you would need one or two qualified sailors. Next thing I would get a Leewards guidebook which will answer most of your questions. The sail is about 100 miles with many great islands in between. You could encounter some big open water sailing.

If you can find a charter company that will allow a 1 way trip it is an enjoyable time during a 9 day sail - a day or 2 exploring Antigua then about a 35 NM sail West to Nevis and clear in at Charlestown where there are nice moorings for a day or 2 - an easy sail over to St Kitts for another day or 2 - about 20NM to Statia for an interesting overnight and a nice 30 NM sail North to St Barths for at least a 2 day stop then a daysail over to St Marteen - some good open water sailing but almost always line of sight but with some careful planning for departure and arrival times no difficult passages - barring bad weather of course. A good cruising guide is a necessity and with a lot of new harbors to navigate a lot of attention to charts is paramount. Clearing in and out of so many countries along the way on such a short trip will really take more time than you realize though. It is an ambitious itinerary with a lot more time underway than most people would care for on a vacation IMHO. People looking to really do some sailing would love it however. Bareboat restrictions on night sailing will mean some dawn departures for sure to allow for good afternoon light entries on the longer passages.
I have sailed those waters a lot in the last 40 years and early Dec. can get breezy and I would want to take more time to cover that amount of distance and enjoy more time stopped along the way than a 9 day trip allows. Everyone aboard should be sailors and the Captain should be an experienced sailor! - For a vacation ---- doing this trip on a crewed charter boat would be a much better experience for everyone involved and much easier to book with a Charter Broker.

Horizon in Antigua does this and I believe charges $700 for the one way, which is a bargain. It is a slog heading back to Antigua, but very easy going the other way. Very easy to to Antigua, Barbuda, St Barths and St Martin, but you will be rushed every stop as you will lose time sailing between. It is 4-5 ANU to Barbuda, 8 hours Barbuda to St Barth etc. I would always leave Barbuda at Midnight to arrive first light at St Barths. Horizon allows night time passagemaking.

Horizon is probably your best choice for that trip.
They have a base in Antigua and St Martin.
We did that trip a few years ago. Just two of us on our Bavaria 50. I think all in all we cleared in and out of 7 countries in a week. Didn't have much time for anything other than clearing in and out, but it was fun.
USA to Antigua to St kits, to Nevis, to St Barts, to St Martin, To Anguilla, back to St Martin and then back To USA.

I would love that trip but for some less enthusiastic sailors it may be a bridge too far - make certain everyone is up to the trip. Antigua to St Martin only, it would be a real slog the other way as stated before. The cruising guides will tell you what you need to know about clearance requirements - expect to do a lot of it! I wouldn't plan to do too many exciting things on land, this is going to be more of a sailing trip if you only have 9 days.

As I recall Horizon would be the most flexible as they are already setup to do this. I noticed Dream Yacht charters has some one ways from various bases Dream Yacht One Ways so you might ask them about your dates. I have also seen some interesting offers from Latesail's SailOneWay program LateSail One Ways although they have nothing interesting right now in the Caribbean but it won't hurt to ask. I think many of these are basically repositioning trips so you'll probably be going the hard direction but I have seen a few over the years that looked interesting and some very good discounts but they usually don't give you much time to enjoy it. Don't know if you can add more days so you have more "enjoy" time on island or not.

The other thing of course is the weather you get. I've put myself in the position twice of having to go just to make a deadline. I wouldn't go if it was dangerous but the admiral struggles on long rough slogs, it wasn't the "vacation fun" I wanted her to have. So, now I try to keep a lid on pushing it and at least put a few days in the schedule to wait out unfavorable weather.