If you're looking for advice, I'll give it. Don't go with the infiniti, not because it's any better or worse than the SHO, though...the NA infiniti? No thanks. I'd want the turbo version, or nothing.
Don't go with a "sorta" better car. Ask yourself, what do you REALLY want? Drive the SHO, put a little into it each year to keep yourself entertained, and sock money away for the thing you really want, like a thumping V8 CTS-V.
I'm rocking the SHO because it's 4 doors, huge trunk, solid Dad car. But make no mistake, I'm socking away money for what I REALLY want...I just need, to, like...make up my mind on that, lol. Ever since it came out, I've wanted a 6th gen Corvette Z06. But...I also really fancy those Chevy SS with the LS3...and I'd super charge it. But then, I also really like the look of the 370Z...but then that was before the NEW Z came out, with the TT V6.
Sigh, so many choices...But I've got time. I'm hanging onto the SHO for at least another 2 years, give or take.