In this particular case it really doesn't matter. Both do pretty much the same thing. You can see the quotation mark idea as if sending keystrokes to the command-line, while the sending integer values idea "may" send the value directly or it may first convert it to a string in any case. I'm not exactly sure how ACad has implemented this, my guess would be that it converts to text - would make the command line interactions easier to program on their side.
If this is the case, then sending a fractional number may vary from machine to machine. Depending on how many fractional points are set to be displayed. In which case sending a text string becomes more controllable from the code's side. If it's not the case (and ACad actually just sends the number value direct into the command without conversions) then the number idea would be the most accurate.
Of course, just entering such direct constant values isn't very interesting. It's when those values come from some variable when this makes a bit of difference. Do you just send a fraction value direct? Or do you convert it using something like rtos so you can control the accuracy?
Personally I've not bothered too much - it seems to work fine for those cases where I had to use the command line interface (doesn't happen often). I generally prefer using direct function calls instead of sending to command-line anyway (if at all possible), either through such methods as entmake/entmod or through vla. None of this "guessing" what happens, tends to run a LOT faster, and is able to be done through ObjectDBX on non-current DWG files as well.