They can both do pretty much do 98% of the content in the game
for magplar slap some deadly strike rings, necklace and weapon of choice on there and your jabs will tear stuff up as well as the jesus beam

the only place it will fall apart as it were is the max end content (vet trials) in which you'll need to two bar to keep up damage wise

I main a sorc and my 2nd love is templar. As has been said here already both are viable it's just mainly how you wish to play. Keep in mind though zos keeps making Sorcs pets "necessary". Flap flap flap flap has had me take breaks from my sorc many times.

I play both as heavy staff attack builds, without oakensoul.
Without oakensoul, you need a different source for the buff Empower (heavy attacks +70% damage).

On my sorcerers, I get it using the set "Elegant" (formerly called Queens Elegance), an overland set from Auridon.
Templars have the skill "solar barrage" that grants empower.
I personally like even more Dragonknights currently, as they have a skill "molten armaments", that grants Empower and major sorcery.
For templars and DKs I use the set New Moon Accolyte for more raw damage instead of Elegant, as they use their skills for Empower, so don't need Elegant.

The second set you use is Sergeants Mail, a heavy attack dungeon set from wayrest sewers.
A monster set that works nicely, is Sellistrix (Arx Corinium dungeon), or Slimecraw (Wayrest Sewers).
I use 5 pieces light armor for high penetration, and chest and legs heavy to survive worldbosses. All divines, health glyphs.
Infused lightning staff with flame glyph, bloodthirsty or infused jewelry with spell damage glyphs.
Mundus stone: the lover.

Such a setup is not as strong as an Oakensoul setup, but easier to play for a senior like me (57) than a light attack rotation, and I still can solo several Worldbosses like in Northern Elsweyr.