I have found that in 5ed I tend to just run two troop choices. I like really hard hitting troops. My Khornate daemon list features two squads of 15 Bloodletters and my current Blood Angels jump list features a full assault squad and one squad of Sanguinary Guard (Dante for an HQ). I see that most players like to run more - typically anywhere from three to five typically. I am comfortable with only two and if I feel hard pressed with my Blood Angels I can always combat squad the assault Marines. The way I look at it if you are playing rulebook missions there is only one mission that features more than two objectives. Obviously this is not always the case with home grown missions at tournaments. The only major drawback I see to running two troops is that it's going to be hard to massacre for missions that feature three or more objectives as the primary goal. The good thing for me and my philosophy is that some people are now advocating the use of W/L versus W/L/D; i.e., massacring could become a relic.
I like to run only two troops because it is the minimum required - this allows me to take other units that in my opinion have more flavor. Sure lots of troops can be very powerful. For example, ork hordes with lots of shoota boyz is nasty. Same thing can be said for Tyranids featuring Tervigons and gaunts. The thing is though these two armies don't seem to be winning any tournaments lately. It just seems like hordes is not that great when it comes to 5ed and the way things are playing out now. CSM I think have it the best when it comes to scoring units - Plague Marines and Berzerkers are very solid choices. Scoring units for other armies can be a problem - look at Tau and Eldar. Going back to W/L versus W/L/D and the elimination of battle points there are some smart people saying this will help these types of armies to be more competitive. To me that is interesting and I'd like to see how it all pans out.