Also, the type and energy efficiency of the systems you install in the home can definitely come into play here. For instance, electric resistance type baseboard heaters are typically very energy inefficient. However, electric heat pumps can be very energy efficient and electricity in this instance can be cheaper than natural gas. There are a lot of new "green" energy efficient systems available these days so you may want to do your homework. If you contact a local mechanical/HVAC contractor they could go over some options with you.
The builder may be pushing you towards electric baseboard heat because they are very inexpensive systems and really easy for them to install.