Don't underestimate the intensity and killer attitude of the Islanders to take out opponents during these Stanley Cup playoffs. 
The Islanders took out Washington, a team with far more firepower than Philadelphia, in five games during the first round while the Flyers were being outscored and struggling with the inferior Canadiens. 
Now the Flyers are down 2-1 in the series to the forechecking, disciplined Islanders. The Islanders play the Flyers' type of game except better. 
Philadelphia has scored just 16 goals in nine Stanley Cup games, an average of less than two goals per game. 
The Islanders have outplayed the Flyers for the past five periods. So I see no compelling reason not to stick with them.