What would be the recommended route to upgrade UCS firmware on a environment current running 1.4.3x ?
would it be better to go from 1.4.3x to 2.0, then to 2.1.
or go straight from 1.4.3x to 2.1x ?
Since you're currently at 1.4 you can directly upgrade to 2.1(2) - latest release if you wish. This process can be made especially easier using the Firmware Auto Install feature of 2.1.
Review the full upgrade procedure, but essentially you'll first download the new 2.1(2) "A" and "B" bundles to your UCS system, then activate the UCS Manager image first to the new 2.1(2) version. After UCSM restarts you be able to use the Firmware Auto Install feature to upgrade the rest of the Infrastructure (IOMs, and FIs) and then the Server endpoints firmware.