It gets down to how much do you want to spend and how much are your using it, I have two lasers, always have had two, a cheaper one, and another high end laser, to be honest I like the cheaper one better, a GL422 dual slope laser is about the handiest I have found, it does it all and has its own remote too, which is really nice once you have had one, saves a lot of time chasing and changing grades on layout work and figuring estimates, but most important, is the weight of the laser. If I have to lug one around all day long constantly resetting it, I'll take the light weight one any day, also works on a lighter tripod and which is nice to save having to drag out the heavy larger tripod all the time. My high end dual slope is the GL722 I think, which is an excellent laser for when I'm running a machine control and need something that wind doesn't bother as much, which brings about the discussion of tripods, heights and uses you'll have for one.
As for receivers, I've had many, for machines I use bullseye's and for hand work, the small receivers that come with the laser setups, the hand lasers, don't ask me to quote numbers on them, but the one that came with my new 422 is really nice, it shows how many inches above or below grade you are by looking at it, its in digital readout, is great, my crew just loves it, saves having to mess with the grade rod to lower and raise it constantly to tell how many inches your off grade, the receiver does it at a glance, far better than the cr600 that came with my last two lasers, an older single grade and my 722.
It gets down to who fixes them for you, and what features your wanting in a laser and receiver and how in debth you want for machine controls or plan to go for them in the future. I'm not sure if I helped you or not, I'm not the tecky type, just have personal preferences of what I like and why, the single best thing you can do if your not used to using a laser is to either beg, borrow, rent, steal or get a demo of several different lasers and receivers before buying one is my advice, then go from there.