So, lets compare those items:
Scaled Drakeskin Chestguard: 47agi, 102ap, 25haste rating, yellow socket. Lets gem it with 8 agi to get: 55agi, 102ap, 25haste rating
Beastmaster Curiass (your current item): 40agi, 48ap
So yes, to your blue breastplate this is a huge upgrade.
However there are quite some other breastplates around which are nice for you as well. E.g. lets have a look at
Hauberk of the War Bringer: we gem it with 3x 8agi since you are survival specced: 48agi, 76ap, 20haste rating.
Obviously the badge breastplate still wins, but the margin is not that big anymore (still 7agi, 26ap, 5haste rating). If you want to have that thing, go for it, but there are a lot of places where you can upgrade your current breastplate.
SV hunters however have a really hard time to get decent rings. To my knowledge there are 5 very good ring for a SV hunter:
- Garona's signet from Kurator
- A ring from handing in Magtheridon's head
- The badge ring I recommended to you
- A Sunwell BOE craftable ring
- The Mount Hyjal reputation ring (which is great at exalted)
With the badge ring you get the 2nd best ring that is currently in the game (only beaten by the mount hyjal exalted ring or perhaps the Sunwell BOE craftable ring if you need the haste rating). That is the main reason I recommended it to you.
Lets compare your blue ring with the badge ring:
your ring has: 13hit, 21crit, 24ap
the badge ring has: 29agi, 58ap, 126armor ignore
While it hurts to lose the hit rating you will find enough good items with hit rating in Kara. Soon you'll be way above the hit cap and wonder where you can exchange it for better stats.
The 126armor ignore are roughly equal to the 24ap on your blue ring.
Thus you basically exchange 29agi and 58ap for your 21crit rating (and till your hit capped for 13hit).
That is also a huge upgrade and as I said before you won't get many upgrades for your blue ring (though there are some other blue rings which are a lot better for a SV hunter than your ring is).