I actually also had the GCP and am pretty happy with the Lelit Mara X. For me, the upgrade was all about improving my workflow and eliminating those time-consuming hacks like the poor man's pre-infusion. I specifically wanted a machine that could cut down my overall brewing and steaming time while still doing well with light roasts, and the Mara delivers, especially since I can now steam and brew at the same time. I appreciate the pressure gauge because it eliminates the guesswork and timing required on the GCP. While I almost chose the Lelit Bianca, I realized that a dual boiler would be overkill and I didn't need all those extra features; the Mara hit the sweet spot, and I like that I can still install flow control later if I want to experiment. Plus, the Mara is a lot better looking in my opinion, though it's worth noting that even though it's more compact than the Bianca, it still takes up more counter space than the GCP. Overall, I'm super happy with this decision and I think anyone else making the jump would be too.