I've used both extensively and I think they are fairly different, with different strengths and weaknesses. Bash is more pragmatic and more concise on the command line. PS is more uniform in its design and nicer for scripting IMO. It allows passing objects through pipes, has built-in JSON reading and writing, built-in parameter handling with defaults, mandatory and optional params, switches etc., and such niceties.
Bash is not more concise, its other way around, of course, if you use default aliases. The reasons is logical - you almost never use text parsing in Posh while you almost never have anything without it in bash.
