In my opinion they are fairly close, but both have commands available to one and not the other, for example substring command is not supported in sh but is in bash ${TEST:$i:1} For arrays, in /sh you use the following syntax

${array} - accesses element 0
${array[i]} accessed element 0 - 1023
${array[*]} and ${array[@]} -uses all elements of the array (list), the difference in the two is that one set is quoted and the other isnt
You can skip the ${ } syntax in sh by using (( array[ ] ))

Personally, I think sh (actually ksh) is better suited for scripting (some may disagree...like I said, just my opinion).

If you want emacs set your EDITOR variable to use emacs. /sh by default uses vi...pretty easy to use once you struggle through the command syntax!!! Use set -o to see what options you have turned on.

To get your history, use ESC-j or ESC-k to scroll up or down. command expansion, hit ESC twice to expand what you are typing on command line. Like bash, you can use / to search your command history.

Plenty other differences Im sure, pick up O'Reilly - UNIX in a Nutshell to see all commands specific to sh.