I got my 4.88s for my diffs from Just Differentials...great guys to work with. For skids there are two schools of thought...
1- buy the best you can afford in steel as you will never have to worry....
2- buy what you will need for 80% of the stuff you will encounter and dont pay for the extra protection you may only need once or twice in a 5 year period.
both are worthy and good choices as it is really a personal choice....
on previous vehicles I went with steel skid plates. Good Points-----they are Heavy duty protection....easy to repair if needed with big fxxxing hammer and some welding skills but never had to repair anything. Bad Points----they are HEAVY. Between heavy tires that are 50-75% heavier than stock plus have higher friction on road surface than OEM.....steel front bumpers with a heavy winch and steel cable....heavy rear bumper with hi lift and spare tire...plus all the gear we carry for offroading...it really hits your gas mileage...big time. You also have to make sure you match your suspension for the constant load you will have every day not just in woods and it reduces your PayLoad for your personal stuff on trips...as truck cant tell diff between all your heavy steel and your wifes makeup and lingerie in the back on a trip.
The aluminum....I know somone that wheeled the snot out of ASFIR skid plates...front to back on an FJ Cruiser. She wheeled MOAB, Colorado, Rubicon, etc. They were gouged, grooved, bent and beat up after years of abuse but still held. She recently gave up and went to steel but she thrashes her FJ Cruiser in places nobody I know would go...then again she took doors off and has the tube doors on it...and it is set for rock crawling...she goes by Athena on the old blue forum. met her in Ouray and checked out her rig and it was beat to hell underneath but the skid plates were holding up with only a couple places really needing attention.
For that much abuse I dont think we could do anything to them here to come close to what she put them through on her FJ Cruiser. GOOD POINTS--- light weight, easier installation due to weight and aluminum has a very high strength to weight ratio. BAD POINTS---- good bit MORE expensive for same items...so have to decide if weight savings and any benefit from payload or MPG is worth the extra cost over expected life of skid plates. The only other bad thing I have heard from Athena is that on some rocks you dont slide down with your momentum like on steel as it has tendancy to grab more on the rocks...so might get high centered more until you learn to come with a little more momentum if you know you are going to scrape a big rock underneath.
If you got the money...the aluminum will take all except the MOST hard core hits...
If not, then instead of paying up front will pay over life of skids with the extra weight...
The choice is yours..

Glad we could make that easier for you...hahahaha