I think the G5 is a tad different from the other two that you mentioned. I had the S400, but returned due to the lack of manual features it had. I think it also depends if he is going to be taking a lot of ordinary point & shoot photos..if he is then i would go with the S400. If not, then the G5. The G5 has many manual options, but there is quite a differnce in price between the G5 and the S400.
I ended up ordering the G5