"Personally, I think par-4 holes are the backbone of a course, and I wouldn't want to build a course that only had six or eight of them.
However, whenever I've tried to think how to make a course that would be exciting for a professional tournament, I keep coming back to having more par-3's and par-5's. The extra par-5's would be because I want the players to hit long clubs into the greens, and no par-4 at any length does that to the pros. So my 540-yard holes would be reachable in two, but I think you'd have to call them par-5's, and then you'd have fewer par-4's."
TomD:
For some years now I've felt that some courses can very easily do both and for basically no cost. They can do it simply by two scorecards that call some of the same holes different pars. The ones that can do it best, in my opinion, are the likes of NGLA with it's original par 73, or GCGC or Maidstone with it's par 72 and #15 and #16 being sort of half pars anyway.
Those three courses are good examples of the club being able to just create a par 70 course for all of them for the crack player and they can do it without doing anything to the golf course itself, just the scorecard. Think about it.
I finally got my club to create a championship card for the good player calling our #18 a par 4 and the course a par 70. For the rest we still have the par 71 course with #18 a par 5.
One might even call this "par skewing" because players may actually try to play those holes differently even if nothing is actually done to them other than designating them a different par on the card.
And some years ago I strongly recommended what Scott Warren just said---eg just have a single gross score course par and no hole pars and let players just play the holes the best way they think they should strategically with no hole par consideration to influence them.