My observations have been this, from the start, consistently (including with Omen traits before potions)
If you have any explosion at the start of battle, but no storm, you are likely to be in a less advantageous starting position on average because 4/5 matches are actually more common at battle start than with randomly falling stormless configurations (likely due to the slightly lower incidence of skulls on starting boards vs what will skyfall even with no storms making it slightly more likely that any random configuration of gems will contain a 4/5 match). TPK use is a huge example of this. You’ll also have slightly less (not skull) empowered converter alignment. Mana gain might be about neutral over time on the first match, but empowered converters, match traits, and cascades skew the advantage of having your “slightly less balanced” board more. (However, as I stated when I first did my examination of potions going through all the scenarios, enchant advantage generally makes up for this, and allows for team builds that wouldn’t have been viable otherwise)
If you have a storm set up, and 2 or more explosions at the start of battle, you’ll generally make up the difference with cascades (sometimes a lot of mana, a new 4/5 match which might lead to lots of 4/5 matches, or both, rarely purely a comparative disadvantage). If you have just 1 explosion and a storm, its about a wash on average.
So in my experience, over time, these four explosions trend toward strongly advantageous if you are starting with a storm, and weakly disadvantageous otherwise (but not so disadvantageous to outweigh the advantage of having enchant).