Well, which is easier to say, "Your sins are forgiven" or "rise and walk"? They seem about equally easy to say. Of course, Jesus did not speak English, so we cannot have a truly informed answer without comparing the original Aramaic phrases, which are lost to us. Even a scholar of Aramaic could only guess at what was originally said. Was one phrase more of a tongue twister? Neither will be many more syllables in any language. One includes a noun and a verb and the other two verbs and a conjunction. But whoever translated Jesus' words into Greek, whether Q or Matthew or a theoretical translator of Matthew, did not think that the original language had to be preserved for understanding the point, so we can comfortably answer the question then. Which is easier to say? It does not matter.
Since neither is easier to say, then Jesus' question implies that they mean the same thing. The Pharisees want to suggest that, while neither is easier to say, the healing is much easier to do. Jesus is telling them that he never heals except when he forgives sins. This bothers us modern people. We have rightly rejected the idea that sickness and sinfulness are correlated. Neither are the sickest the most sinful, nor are the most sinful always sick, and what of innocent children? However, just because sickness and sin are not strictly correlated does not mean that they are not related in some way, that the sinfulness of the world and the sickness of the world go hand in hand. As our first reading and tradition agree, in heaven there is neither sickness and death nor sin.
Jesus looked at the person on the stretcher and knew that while his body was disfigured by sickness, his soul was more disfigured by sin, as all our souls are. Though the crowd saw a man who could not walk, Jesus saw a man who could not love God. Any doctor could explain that to heal a lame man so that he can immediately stand up and walk would require many healings, of nerves and muscles and blood vessels. When Jesus heals, he does not name every healing individually but only part of the healing, and, without doubt, the central healing that every one of us needs is the forgiveness of sins. No healing, be it ever so amazing, would be complete without it, and Jesus would never heal us incompletely.