Cheaper to use a drone for spotting instead of a FIST unit. That's what's working for the UA.

Kamikaze drones have a role for the smaller units, but at the battalion level, it's better to use a surveillance drone to coordinate fires from mortars, MLRS and artillery. The rounds fired from these systems typically have longer range than a drone, a higher rate of fire, and larger warheads.

In fact it seems to me that overall drones as artillery spotters have been much more impactful than direct fire drones in this war.

Yes, except for the strategic things like hitting AA, ships etc..

Artillery is the king of battle. I've seen numerous SAM/AA gear destroyed in Ukraine by artillery using drones for spotting.

I think these are pretty complementary. Switchblade 300 is a 10km range Javelin (same warhead in fact) with integrated surveillance capability that can go beyond range of sight. It is not there to replace mortars, artillery and MRLS, which are area weapons.

switchblade 600 has the Javelin-like warhead, switchblade 300 has something equivalent to a 40mm grenade for a warhead

The 300 is the low collateral assassination drone when you can't use sword bombs.

The switchblade 300 has the same warhead as a javelin? Got a source for that?

It's the 600 with the tank buster.

Artillery has been used by Ukraine, and by a lesser extent by Russia, extremely effectively as a precision weapon against all kind of targets, including MBTs.

You can survey with a drone. Merging the observation with the munition is what makes it a loitering munition, but drones for observation/targeting/correction + traditional corrected or guided artillery is very similar (especially guided shells like Excalibur etc which are also themselves similar to loitering munitions just that they loiter very briefly…)