EdvinW wrote: "Not necessarily. Depending on how you feel about bending and what you want in terms of chords, the one in G might be better"
I just wanted to add that if you are on the fence on focusing on this matter, and you tongue block and play splits, etc, I would lean toward the G. The chords tones that you will get from a PC tuned harp (and a PowerBender harp for that matter) open up a lot of variety.
I also agree with Triona, as in get them both. I have the G and D stock PC. Then I have a G that I tuned to C awhile back. Between these three, I have tons of options to dial in the "feel" of what ever song I am playing. I would love it if these were available in more keys, as this tuning, coupled with PowerBender encompassing about 95% of my playing now.
Another way to choose might be to think on the modes. If the style of music you are playing, or the song itself, lends itself to the Mixolydian mode for example, then the G (which is D Mix) might be the way to go.
For an example of this see(I am quoting a relevant part below, see section 2.3.8):
http://bklondike.e-monsite.com/pages/we ... style.html
"Occasionally, and quite effectively, they do play in the second position (Québécois melodeon players refer to playing in the second position as “playing in reverse”). The second position lends itself particularly well to some music, such as Irish polkas, imparting a certain energy to these tunes and allowing some ornamentations(sp) to be fluidly played on either all draw or blow notes. “The Wishful Lover,” played by the Murphy family, is a good example. Just for the heck of it, get out of the “first position rut” and try playing a tune you know well on one harmonica in a different position on another harmonica. It’s seldom possible (and when it is, it may give you a headache - so have a bottle of aspirin ready). By the way, “Hommage aux ancêtres” is scored in the key of A but is played on a D harmonica - in the second position. Once you learn it on that harmonica, learn it on an A harmonica - in the first position. This tune is an excellent example for illustrating the difference between positions and modes. In either position, it’s in the same key, A (F#m), and mode, aolian(sp).
"Without delving too much into the concept of modes, most tunes in this book are in the “ionian” mode : their “root” notes are the same as the key of the harmonica used to play them. On the other hand, “Reel de Village” and “Reel Levis Beaulieu” are in the “mixolydian” mode : their “root” notes, A in each case, are five tones higher than the key of the harmonica used to play them, D in both cases. Thus, the chords that accompany these tunes are those generally played for tunes in the key of A. The first two parts of “Reel Béatrice” are in the “aeolian” mode: the A root note for both parts is six tones higher than the key of the key of the tune, which is C."
They are talking about tremolos v blues harps, but the analysis of modes should be the same. This also gives you some insight as to the what Québécois melodeon are doing. They are playing diatonic instruments (I think), so it might be a good idea to takes cues from their approach.