i had this very same question and discovered that there are only 2 programs in EM that are MD/DO..
what you need to find out is if the program is truly ACCREDITED by both the AOA and AMA..you do this by picking your specialty, looking on AOA opportunities page and cross refrencing the list with FREIDA...you then call the individual progarms and ASK them if they are dually accredited..many programs will list it if they are b/c they want to lure you that way.
you will not however be increasing your insurance carriers, etc..DO's are fully recognized everywhere but louisianna and i don't know of any insurance carriers that don't carry DOs..
you WILL however, run into problems trying to bill for OMT if in fact you plan to do family practice with a lot of OMT. there currently are not very many techniques which are accepted by insurance carriers..it does not matter if you put MD after your name, they still will not accept it.
sitting for both boards is nice, but not always necessary..for example, in EM, i can still be a full fledged fellow member of ABEM and ACEP without sitting for the MD boards..
so, research carefully before making too many sweeping generalizations.
keep in mind that your status as a DO is not really restrictive in practice, only in politics.
good luck