Xamarin vs Firemonkey. What do those who have tried both advise?

Question

Xamarin

In light of the current free Xamarin, I'm interested in the advantages / disadvantages of Xamarin and Firemonkey for transferring a serious CRM application with a bunch of tables and windows from the VCL.
I started with a simple application on Firemonkey - everything seems to be fine now (Seattle) (In XE6, even just a form with a calendar already slowed down), but compared to VCL, Devexpress components are severely lacking, especially QuantumGrid. There is only a pathetic buggy similarity from TMS, with which there is no desire to mess with.
But with threads, everything seemed to work on all platforms.
In Xamarin, I looked that there are tables from Devexpress, but I don’t know how things are with everything else.