I also agree with @mfro
Altera has always had better documentation compared to Xilinx for comparable products IMO. Altera has been better at providing usage examples and waveforms, whereas Xilinx often just supply a little text and expect you to understand how something works (then you often need to contact support to find the real answers!).
Im not an Altera user now, but with the way support has been going, apart from trying to align support across intel, the plan does appear to be similar to Xilinx: No support requests for low $ users, support engineers in the forum and fewer FAEs.
Vivado is still a terrible buggy mess (especially with VHDL) with very limited feature support compared to Prime Pro.