I don't think anyone can tell you what your best bet is, since no one knows how your home is constructed and where in MD it might even be located. Still, you should get some replies from those that have way more knowledge than I.

Now I can tell you I grew up around Baltimore and a heat pump was all my parents had back in the day, and it was enough for cooling and heat, except on the coldest days. But this was a house built in the mid 70's.

These days, most new homes, in the area, are equipped with a gas furnace and AC. I currently have a propane furnace, and AC, but am replacing the AC unit with a heat pump. This will give me a dual fuel (Hybrid) setup.. so unless it's really cold out, I'll be using the heat pump for heat... As for size, I'm in a 2400 sqft home (Excluding the basement) and have a 3.5 ton condenser and a 100K BTU furnace... The 100K furnace is over kill, but that's what the builder put in... Oh, last thing... when my home was built in 2004, it was a EPA Energy Star home, so my home is every well insulated... I don't get any stink bugs in the house... If that says anything...

What kind of oil heat do you have that is not "central"? The most important question is if natural gas is available. If you go with a ducted system, be sure to put the ducts inside the house envelope if that is possible. Ducts in unconditioned areas are asking for inefficiency at best and poor air quality at worst. Consider mini splits if indoor ducts are difficult and gas is not available. Mini splits are most practical if you have an open floor plan because you have fewer units to buy and maintain.

Why not get a couple of HVAC contractors to stop by and give you an estimate? They are not busy this time of year. It they give you several options, you can post them here for comments.