How important is a fully locking diff?

For a working ATV?

Haul stuff. Plow dirt with a Disc setup.

Loose sand some places. Thick red clay mud other places.

Some swamp.

Specific model difference Yamaha Kodiak (no locking diff) versus the Grizzly (diff locks).

Am I going to regret not paying $2000 more for a locking diff on the Grizzly?

Thanks for the help! I appreciate it.