The main argument for Energizer(for me) is that it's free stats period. Impulse Thrusters might technically be free stats, but it is going to encourage us to add tonnage when we don't need it because we'll be able to hit medium maneuverability a lot more easily.
I know I personally have been harping on about how better thrusters allows us to justify increased tonnage but our last design straight up settled for
medium tonnage and
low maneuverability because of how cheap the design would be without the extra mass or thrust.
In situations where we want to field a lot of ships we are going to want to keep costs low and thrusters have shown themselves to be quite expensive so keeping those to the bare minimum while retaining good cost and maneuverability will be critical if we want a ton of ships that have a decent tactical rank (we absolutely want this given the looming Klingon war).
Ironically, you could more easily justify slapping extra thrusters onto your bleeding edge exploration-battleships vs your cheap workhorses as you aren't expected to build a lot of them anyways and as such the cost of individual hulls is much less of a concern compared to a ship you need to pump out a ton of.
I've brought this up in previous posts before but maneuverability has a huge influence on how much a ships torpedoes contribute to the ship's overall tactical rank.
To put it into perspective, if we had gone with 2 torpedoes and 4 phasers for the Kea (which would have still costed more industry than the Saladin) which would give it 75% phaser coverage, equal alpha strike, and double the Saladin's multi-target rating (8 vs 4) it would have still been a whole grade worse in tactical rating than the Saladin thanks to the Saladin's medium vs the Kea's low maneuverability.
This is also supported by the fact that even with torpedoes the low maneuverability meant that the Kea's tactical score would only get bumped up to the marginally superior A rank over the Saladin's A- in spite of the Kea have nearly twice the Saladin's phaser coverage (100% vs 54%) and 3 times the Saladin's multi-targeting capabilities (12 vs 4).
And also to ship survivability.
Superior maneuverability meanwhile allows the Skate which has less than half the mass of the Stingray (30kt vs 70kt) and only 1 rank more maneuverability (VERY high vs high) attain an equal defense rating of 12 for each.
If the Kea for example had had
medium or
medium-low instead of
low maneuverability it would have made fitting torpedoes from the get go massively more justifiable and probably would have yielded an A+ or S for tactical rank at launch if we kept the phaser loadout the same (alternatively the better maneuverability would justify less phasers and thus less industry cost). That would have undercut a major reason (Saladin is shootier than torpedo-less Kea) for building the Saladin which may prevent it's design and lead to more Keas which would give Starfleet a lot more viable long term science vessels since the Saladins did not last very long as a science ship (30 years vs 81 years).
Looking at our current roster of ships we are almost certainly going to be designing a replacement for the 50+ year old Cygnus soon which given that the Cygnus was our generalist workhorse is going to mean we will need to build a ton of replacement ships and that is definitely a ship where I would want to squeeze as much performance out of a limited number of thrusters as possible.
While the Klingon war, if it does happen at the specified time from the Kea update is still some +50 years away that same review noted that both Kea and Saladin class ships are still active during the war so any future designs we make will want to either be able to run away or have a decent tactical rank capabilities for when that war happens, both of which better thrusters would contribute a ton to.