Advantages: Unified design, designed to work together as one.
Disadvantages: Can't swap to another Atty or Battery size (in many but not all cases)
Reality: Hybrids are awesome but so are mods and atties. Not much practical difference between them. In the case of Zenesis Hybrids, they've been around a while now but you'll still be hard pressed to find a better looking device on the market.