Well you are going to get many stories on hosting programs, best thing to do is to download all the demo's and try them out for yourself.
I hated PCDJ/KJ due to it being such a resource hog, my personal preference is MTU Hoster. I like the fact it's a fully self contained program over most of the others that need a couple other programs added (at extra expense for some). Hoster is the player, plays outside CDG (like customer discs) without the need to rip them to the computer, builds the songbooks based on the database and rips them - it does use a propriatary format however if you rip to mp3g, it will still play & catalog them just like it's own format - but for this you will need an external mp3g ripper. It's also nice because it plays/catalogs video files (big plus for my needs as well). It has everything I need in a program & more is on the way this coming year.
I have never had it crash during a show, over 3 years now. Have run 8 - 12 hour shows non-stop with no issues.
Again, it's my preference. Not going to say it's the best like many will with a certain other - there is no 'best', it's what will fit your needs, be reliable & how easy it is to use - it fits my needs with extras! Plus very easy to use.
Buying a laptop on the program specs is smart, but 'most' laptops today are more than capable of running a show - just make sure it has dual screen capability where you can extend the desktop to a second video source - for the words. I would highly recommend to plan on an external sound interface, it will bring the sound quality up ten fold! Look into the Lexicon Alpha for this.
http://www.zzounds.com/item--LEXALPHA
Cheapest it's been in a year, I paid $99 for mine when it first came out.