The NL East this offseason just became as competitive a division like the AL East. Where I would start to gauge the possible advantage one team might have over the others is to look at the starting rotation:
Washington: Scherzer, Strasburg, Corbin, Sanchez and maybe Ross or Fedee
Atlanta: Foltynewicz, Newcomb, Gausman, Toussaint, and Teheran
Philadelphia: Nola, Eickhoff, Velazquez, Pivetta, and Eflin
New York: deGrom, Syndergaard, Wheeler, Matz, and Vargas
Miami: Who cares?
Next would be an evaluation of defense and the offense. So just on starting pitching alone, I'd give the edge to the Nationals to stay competitive and quite possibly win the NL East (for now). What the NL East teams have done this offseason, however, is put the NL Central and West on notice that the wild-card contenders might all come from the NL East this season. It's not a far-fetched idea at this point. But like the Houston Astros faced in 2018 with an improved Oakland A's team, a good Seattle Mariners team and a somewhat enigmatic but still good Anaheim Angels team, having a tough division to play in means you're just going to have to find your wins early and often within the division and then look elsewhere. Houston won 103 games in 2018 primarily on having a record-setting starting five rotation. The offense was good but spotty. The defense was okay, but not spectacular. But the starting rotation was out of this world.
By adding Corbin and Sanchez this offseason, I'm thinking the Nationals made themselves a team to be reckoned with. IMHO of course.