Solar Panels, with their low power generation, are more of a cosmetic block choice to me.
They could provide niche benefits for the following reasons vs a Titanium Generator block:
Solar panels contribute 0 processing power. A way to increase power generation when at a processing power limit.
Lower mass per volume
Lower Hyperspace Cooldown per volume, due to less mass
Lower Hyperspace Jump Energy per volume, due to less mass
Fewer Required Mechanics
Can be built with Iron, when Titanium is not available. I know, unlikely.
Using a single 1x1x1 Titanium Generator block vs using 20x 1x0.05x1 Solar Panel blocks to match the volume:
82.5 MW vs 44 MW power generation
Since Solar panels are actually generating power based on surface area on one side, it is better to make them thin. You can also stack them on top of each other and not lose any power generation. I will use a single 100x1x100 Titanium Generator vs 20x 100x0.05x100 Titanium Solar Panels to match your example by volume.
Left side is Titanium Generator, right side is Titanium Solar Panel. Green is better, red is worse, in most cases. Ship stat differences:
Hull 7.5 k hp vs 3.75 k hp
Mass 400 kt vs 50 kt
Hyperspace Cooldown 86.7 vs 43.6
Processing power 10,000 (10k) vs 0
825.5 GW vs 400.9 GW
Hyperspace Jump Energy 400 GJ vs 50 GJ
Req. Mechanics 34 vs 17
Matching Mass (160 Panels):
Hull 7.5 k hp vs 30 k hp
Mass 400 kt vs 400 kt
Hyperspace Cooldown 86.7 vs 86.7
Processing power 10,000 (10k) vs 0
825.5 GW vs 3.2 TW
Hyperspace Jump Energy 400 GJ vs 400 GJ
Req. Mechanics 34 vs 134
You can see matching volume is more beneficial to Solar Panels in some ways. Less mass is more beneficial for Hyperspace Cooldown and Hyperspace Jump Energy. None of this is even considering ship maneuverability yet.
Make Solar Panels as thin as the game will allow.