Depends what is your preference - speaking for Middle Range earners. There are three quality living area in Navi Mumbai (though deteriorating as usual).
Vashi:
Expensive to rent or buy.Best for commuting to Mumbai South/Central/West.Crowded.Shopping (Mall - Inorbit, Sector 17 market, APMC bargain/bulk buy)
Seawood/Nerul
Affordable stay yet on higher side Shopping (new Large Mall - Seawood Central)Commuting still not so far from Mumbai - Palm Beach road/SIon Panvel Expressway.Good Schools/College like DPS & DYPS.
Kharghar
Well Known for leisure stay: a. Scenic hill surrounding. b. Paradise during 7 months of monsoon through winters - falls,streams. c 100+ acres of scenic central park with huge playground / swings. d. Occasional concerts happen in large amphitheatre. e. Golf Course - open to all not just members. f. Wide roads - however traffic picking up e. Several good restaurants & road side food joints. g. You can see & hear several species of birds.Shopping (Small Mall - Little world & two movie multiplex & another cheaper multiplex, Sector 12 cramped market & Hiranandani market)Academic hub - from Primary to Post graduate - B School, Engineering, MBBS etc - Khargar is also no liquor area (no liquor shops, no pubs) but liquor is available on both ends (Belapur, Kamothe) which is 10 minutes drive.Rentals available from as little as 5k to as high as 40K.Commuting within Navi Mumbai is OK - however to South, West & Central or upto Thane are range between 1 to 1.5 hrs travel time. Till Airoli its 40 min drive.Metro between Taloja, Kharghar connecting to Belapur is under construction - agw, may start by end 2019/ early 2020.