For the Democrats the Pennsylvania has much lower stakes than the Republicans. Hillary essentially crushed Bernie hopes when she drubbed him in New York. However, Sander's campaign has struck a defiant tone an is looking to Pennsylvania to stop the bleeding. Bernie very slim hopes rest on strong wins the rest of the way and flipping Clinton super delegates.
On the Republican side, Cruz desperately needs to halt Trumps momentum that was earned in a blow out win in New York. Cruz is essentially mathematically eliminated, so he is pursuing a prevent strategy as he tries to keep Trump from clinching the nomination before the convention. Trump leads by double digits in Pennsylvania. Cruz will need a incredible comeback to blunt Trumps momentum.