I was doing some math hammer the other day, and LC do better at killing T5 and lower, where as Thunder hammers do more wounds against T6. I'm going to do a pro/con list for you.
LC Pros
Better at T5 and lower.
Benefits from Furious Charge and makes wounding T6 better than thunder hammers.
Strikes first.
Best to wipe mobs
LC cons
Only possible to destroy Armour 10 vehicles and 11 if with furious charge.
only 5++ save
TH/SS Pros
Can kill T6 easier
Can Destroy Armour 14(with difficulty) but 13 and lower can generate penetrating hits.
Storm shield grants 3++ save
TH/SS Cons
Attacks last
weak against mobs
doesn't benefit from furious charge much.
That is all I can think of right now. Basically, kit them to how you will use them.
AKA Th/SS/ for tank hunters(advice against because meltas do better), TH/SS in space marine codices where there is no furious charge, use TH/SS for MCs, If Foot slogging use TH/SS, LCs for horde armies, LCs for taking out armoured units, LCs for Furious charge codices, LCs if in Land Raider.
Personally I think a ratio for 2:3 or 3:2 is best, my problem is I only 5 and I want to be able to change the build accordingly