Don't know anything about Buzz other than KLM low cost op. You could probably find a web site for them if you have a quick look. Haven't seen them at LPL yet.
Emerald are mostly night frt flyers with ancient HS748 aircraft that regularly have minor problems to carry and less regularly complete stoppers.
Pay is not bril from what I hear but if you are new and looking to build hours before going onto something shiny, then that's your place. Many do this. Word on the street is possibly some redundancies (rumour control only, but this is a rumour site!), already got rid of all their base ramp staff. This is quite well known about LPL as they were pretty p***ed off and didn't leave quietly!! Looking out of the window, they do not appear to operate as many newspaper flights as they used to either, but it appears that another operator has started them. Read what you will into that. They also operate for the post office. Would not like to speculate too deeply on that part but with consignia looking to cut costs, would suspect air transport is probably their costliest bit pound for pound of frt carried so it wouldn't take a rocket scientist to see that perhaps some of that work will be transported by road in the forseeable future, What impact that may have on pilot requirements is, of course, only known to them.
Other conditions unknown, ie roster patterns, how often you get shafted on your days off etc, but if I had an offer from both I'd take the other one!
Best of luck
Doc C.