What year are you looking for entry? All of the schools are academically selective and all achieve excellent exam results.
SM (esp Junior School) good for music, GW also good for music. GW also good for sport (but sports block being redeveloped at the moment - no idea of impact). Although all of them are considered good for sport. GH playing fields a bus ride away from the school, SM similar, but not as far.
Fettes has a very high proportion of boarders, EA, GW, GH all day pupils and SM a small number of boarders (25 approx in the school).
Fettes follows a mainly English style curriculum with GCSEs & A levels. The others follow the Scottish curriculum mainly, with a few GCSEs & A levels for good measure Some also offer the IB - F & GW, not sure about the others.
GW, GH co-ed throughout. SM single sex for s1-5 and co-ed for s6, EA used to be boys only and only recently added girls and has a higher % boys.
Some of them are a bit more 'formal' in their style F, EA, others less so. You will find at all of the schools there are pupils from different backgrounds. The visit should give you a feel of how you would "fit in" and which are right for your family.
You may however find that you don't get to choose! GW had places for less than 1/2 that took the s1 test, GH less than 1/4. No knowledge of the others, but it does vary slightly from year to year.