Slitherine

Is it possible that some unit Type generate much faster XP?

Example Leman Russ, a Leman Russ (weapon upgrade) and a Leman Russ Destroyer, at the end of Act 1 my two Destroyers had 10 and 7 Skulls, all other Leman Russ were at max at 3 Skulls....

From what I understand, every unit gain XP at the same pace. It doesn't seem to have a difference between unit classes.

Rudankort wrote: For each skull:
+5 or +5% (whichever is smaller) to unit's accuracy
-2 or -2% (whichever is smaller) from accuracy of other units shooting this unit

Sure but i find it somewhat strange that unit bought the same time in diferent variants and have the same ammpunt of replenish after loosing strength points have such a big difference in xp gaining.
All my artillery units and all my Leman Russ Destroyer units geting much faster xp than the Rest, i tryed to use an Leman Russ Vanquisher, like the Destroyer the main Weapon has 4 hexes range. Both used from the second line, both have equal losses in strength but unequal xp gaining.

So maybe other player have observed the same phenomen.

My command squad was struggling to reach 2 skulls while my artillary were way ahead. I think it has something to do with reinforcing units, lowering the total experience every time? Long range units tend to not take much damage hence the xp gains. Then again my flyers have a nice xp pool, and they get shot up every time. Not sure here :/

Each replenished unit number has only 50% xp as before, hence you should always take care of damaged hit points by R&Ring units as often as possible. A loss of few-number units like vehicles is a noticeable punishment to experience. This is the reason why front-line tanks with frequent losses are often less experienced than some recon vehicles which are less in constant action.
The effect of experience (5% own accuracy/-2% enemy accuracy per xp-skull as far as read this somewhere here correctly) is very noticeable of experiened units. I already had an experienced Salamander Command unit which could endure the beating of an inexperienced SKullhamma Battlefortress.
Give your Imperial troops frequently a breather, as you have often enough turns to complete missions. It's often better to R&R in the defensive than constantly counterattacking as each battle continously reduces the morale/effectivity too.