What role is your sorcerer playing in the party?
For support casters it's a great help
If you are a spell caster who is casting a lot of concentration spells, having advantage on the Constitution save if you take damage, so that you are less likely to lose your concentration, is really helpful not just for sorcerers.
My clerics always get it.
My druids always get it.
Sorcerers who buff their allies and debuff their enemies ought to get it.
I don't want my concentration spells to drop. I want them to stay up.
- Flaming Sphere? Keep it burning all fight long.
Bless? Helps my party.
Spirit Guardians? Keep mowing and slowing the enemies.
Entangle? Slow the enemy down, let my martials kill them. Slow? Debuff the enemy, give them disadvantage on Dex saves.
Call Lightning? Yes. Keep bringing down 3d10 each round.
Haste? Make my martials blenders on two feet.
Wall of Ice? Keep that wall up!
Flying? Keep that concentration up to avoid a crash landing!
This answer shows benefits of the feat I borrowed the graph from that answer to illustrate.
Your sorcerer is already proficient in Constitution saves, so War Caster is an additive benefit. To get an idea for how high your chances are to avoid losing concentration thanks to the feat, you move the target number to the left based on your proficiency and constitution, and only use the blue lines.
- Example: your Constitution is 12 (+1 mod, dashed blue line) and your level is seven or eight (Prof bonus +3) so your move left on the graph is 4. If the DC is 10 (someone just did 20 damage to the Sorcerer) your target number is 6 (nearly
guaranteed). If the DC is 15 (someone just did 30 damage to the Sorcerer) the target number is 11( ~83% chance of success to keep your concentration spell going).
For keeping concentration spells up, War Caster is a good choice all game long.
Numbers wise concerning advantage: if for this ASI you raised your Constitution from 14 to 16, you would get a +1 on your roll to avoid breaking concentration when taking damage. With Advantage from the feat, you are getting roughly a +4 to +5 benefit on a given roll.
Being able to use a spell as an opportunity attack is icing on the cake.
Does this help a blaster-style sorcerer?
If you are playing more of a 'blaster' and less of a 'support' sorcerer then a boost in your casting stat is a better choice (make the spell's DC go up) or if Charisma is already maxed out, a feat like Elemental Adept.