I can't really tell you which one of the hoes you should buy, really depends on how deep you need to be able to dig. I will make you a proposition though,
Buy the 48, if for any reason you don't like it, I'll trade you my 47, and the amount you paid over the cost of a 47. I'll meet you half way.
I don't have any complaints about the 47, but could use a little more reach once in a while. The 47 was on my tractor when I bought it used (24hrs on it), and I didn't get a choice. If I had bought new, I would have gotten the 48.
Have fun with the new rig,
DT