I am in the process of writing a contract to purchase a new lowcountry style house. In all the other neighborhoods this builder has completed fiber cement siding was used on the houses. This new development will be constructed using vinyl siding. My question is: Is there a vinyl siding that looks close enough to fiber cement/hardy plank siding that it will not compromise the lowcountry/charleston style of the house?

It could easily look better, depending on how well the vinyl is applied, and what pattern they use. My complaint about fiber-cement siding is that, because of its weight, it is made quite thin, and it does not produce the strong shadow lines of wood or vinyl siding. Maybe a dutch-lap vinyl would look good on your house...it has strong shadow lines, and it does not have so much of a concave surface as plain clapboard-style vinyl. There is also a premium vinyl siding which has an applied foam backing...it looks the most like wood, but it costs.

Beaded siding also looks great and does not wave as much when installed.
Do not allow less then .042 thick siding to be installed. .045 is better.
90% of any siding jobs look comes from how well it's installed, and what trim is used.
Just adding some dental moulding or headers over the doors and or windows, using beaded wide outside corners makes a huge differnce at little cost.
Check out www.midamericacomponents.com for some ideas on what can be done.