Your employer can file for green card without filing for h1-b. If you have master's degree and your job requires a master's degree you can file green card and you might get your green card within your opt extension timeframe(17 months). Labor approval are usually quick these days. or you can process both h1-b and green card simultanously. if you want to do both together, the best thing is to start your labor for green card first and then process h1b because you have to wait at least  2 months after advertising before filing labor during which you can file your h1-b. 

if you qualify under eb-2 category, i believe the best would be to file green card straight.

but if you have only bachelor's, the best thing is to go to h1-b and process green card.

hope this information helps. let me know if you have any questions.