I am looking into getting some Skitarii to ally into my Cult Mechanicus, starting with just a few - 1x box of Rangers/Vanguard, and 1x box of Sicarian Ruststalkers to start with.

I was wondering which would be more useful - 10x Rangers or 10x Vanguard (or 5 man Squads of each).

also Sicarian Ruststalkers - is it worth it to have the Transonic Blades instead of Transonic Razors, Chordclaws and Mindscrambler Grenades?