We also have the MaxiCosi Priorifix and it is great, Ella is so comfy in it and I love the way that it reclines really easily for when she is sleepy.
The Priorifix is really easy to change from one car to another - we change ours every weekend, but we use the isofix so that makes it easier.
My friend uses a seatbelt with hers and also changes it every weekend, so I think it must be fairly easy.