My co-op has some cheapo SNG caliper brakes which seem fine.. nothing special... dont look snazzy.
That is all they say.. no model number or anything

Would I notice anything by using these calipers instead? They have approximately the same reach.

I dont know what im looking for in brakes really. I just know the difference between rusty/broken and not. What makes one good and another bad?

EDIT: sorry I forgot the link.

You seriously need to upgrade your post writing skills. SNG caliper brakes compared to what?

You waste a lot of energy denigrating people for no real purpose. Keep your negativity to yourself if you're going to answer someone's question. The poster asked about SNG's compared w/ the Tektro 984s, to which they linked. The comparison's to be inferred.

OP, Tektro has a good reputation as making quality brakes. What you pay for with a brake is, first, the quality/strength of the metal; after that, increased cost comes from reduced weight. I haven't had experience w/ SNG's, but if similar in price to the 984s, they're likely in the same range as far as durability and strength, i.e. they won't fail/break unless put under extreme stress (i.e. you're a very heavy rider, slamming on the thing while going down a very steep hill, etc.)

is this something i should be worried about! The SNG are cheaper I have them on my girlfriends bike are they going to explode if she brakes on a hill? shes not heavy but I dont want to her die/explode.
Or is this like 400lbs going 60 KPH sort of idea?

SNG brakes are fine. Tektros tend to be a little lighter and more expensive for about the same braking-performance. With both, you'd want to switch to Kool-stop pads for maximum-performance anyway.

The point of highest liability in brakes is with the cable-fixing bolt. You MUST clamp down the cable with precisely the correct torque. Too loose and you risk the cable slipping under braking. Too tight and you risk crimping the cable and having it snap under braking. Or you may overcome the bolt's yield-strength and it will have little clamping-force. Make sure that bolt is secured properly!!!

After that, braking-power with any brake is determined by the front-tyre's friction limit (provided the rider has enough skill to built deceleration-forces up to that level). If you desire maximum safety for you and GF, then I suggest you practice maximum-braking in a parking lot until you can decelerate from 20mph in 17ft or 30mph in 34ft. That's pretty close to the physical limits of the tyres traction.

Practice building up force on both levers quickly, but don't grab it all at once. It takes about 0.2-0.25s to built up to maximum deceleration. During which time, you want to scoot your butt off the rear of the seat and rest your belly on it. This shifts the C.O.G. rearwards and downwards to fight the weight-transfer to the front and prevent the rear from lifting and throwing you over the bars. As deceleration builds, you'll want to release pressure on the rear brake (while increasing the front) to keep the rear right at the edge of lock-up. There's been plenty documented cases of cyclists and motorcycles sliding into a car with the rear brake locked up and skidding. If they had used more front-brake and not locked up the rear, they would've stopped in plenty of time.

As another test, you can measure stopping-distances from 20mph with front-only versus rear-only brakes and compare to the technique I outlined above.

phew thanks.