Are there differences in protection among safety glasses?

No.

Some are ANSI rated and some are not.

- Note: there are three different ANSI standards

Some are OSHA rated and some are not.

(There is also at least one European rating system, one Canadian rating system, and a U.S. military rating system.)

etc.

Some have ratings from all of these groups.

Better safety glasses advertise their "impact rating" or "impact resistance"

which of course varies from one model of glasses to the next.

Some are especially corrosive-resistant.

Some are especially heat-resistant.

Some are anti-fogging.

etc.

It depends on the materials the safety glasses/shield are made from and how strong they're constructed.  I tested a couple of old safety things I had with my BB gun, pumped up to a level that should be about 800 feet per second.  One was Z-87 rated prescription safety glasses.  The lenses stopped the BB from penetrating, but the bullseye cone that blasted out the back would have been like a shotgun blast to the eyeball made up of powdered lens shards.  Lenses must be made of a strong but brittle plastic.  On the other hand, I also tried to shoot through the face shield of a full face respirator.  All it did was dent, and in one case reflected the BB straight back at me.  That plastic was softer and more resilient for taking the impact of the projectile and absorbing its energy to prevent penetration.

Safety glasses meeting ANSI or OSHA standards only have to meet certain testing limits, and only if they pass those tests can they be stamped with the ANSI Z-87 rating (that of course doesn't prevent counterfeits from China being sold).  That certainly doesn't mean they will withstand all impacts or need to do anything above and beyond that testing.  I'd imagine there are youtube videos from people testing safety glasses of different brands, styles, and prices, so have a look at them to see what's what.

I would go to the OSHA website and search safety glasses. Some think plastic reading glasses are safety glasses but not. We put you on a wild goose chase, when at OSHA search for a bucket of steam and better yet, a tube of relative bearing grease.

I use glasses and a shield when dealing with any possibility of kickback …That’s me …but I only have one eye left (not from a saw, from a knife) so I am a little more cautious.

With glasses you want to look for “Z87” markings on them…that is the minimum standard according to ANSI/ISEA

Cheap brands may shatter when struck by a flying object, not what you want right in front of your eyes. They need to conform to some kind of standard to be worth considering using.