Most of the time I prefer LDC for vocals and SDC for acoustic instruments... but, if you only want one mic to try and do both with, checkout the Shure KSM44.
Please goto http://www.hr-faq.org and read. Also - use the search function above. This question has been asked probably 400,017 times in the past year - meaning you will get nearly 1.32 million responses - 1.15 million saying the same exact thing. Numbers have a +/- polling error ratio of about 17.
I made just one cut with the guitar (Ovation Balladeer) and then one cut with my voice. Might give you some idea of how it sounds on vocals and acoustic.