I find 30-man squads perfectly acceptable. Twenty often feels insufficient and easy to whittle down to inadequacy. Forty tends to be quite expensive, and for me at least, hard to maneuver on the battlefield.
I use two types of blob squads: I like using thirty with a commissar and autocannon teams to hold objectives, destroy enemy transports, and provide bubble-wrap/tarpit screens for my artillery and heavy support tanks. Special weapons tend to be
GLs, or if I have the points, plasma guns. Alternatively, if I have Creed and/or Al'Raheem in the army, I like to outflank a mob of 30 with commissar, armed with meltaguns and power weapons.
Ailaros wrote:
As for the priest v. another squad with a power weapon. 12 rerollable power weapon hits puts down 9 power weapon hits. 16 regular power weapon attacks puts down 8 hits.
Of course, this assumes you get to charge with a large, unwieldy unit with no transport options. And in subsequent rounds the Priest becomes either a 60-point dead weight sitting in the back of the squad, or a liability as he is swiftly killed and gives up a
KP.