i get this question from time to time. there is no right or wrong answer when it comes to collecting anything really.
but i will answer it.
There are three "grading companies" out there that are worth using. thats not just my opinion, but the opinion of most everyone that i know. Each have their own pros and cons.
Pros: Hands down the best protection for your card. their cases are the best. Their Slab actaully survived Katrina. They are the leader in sales as far as post 2000 rookie cards go (in top grade, naturally), and have a stronghold on Cards released after 1980
Cons: if your modern card grades lower then an 8.5, the label they use to put the grade on is almost insulting. its made out of flimsy paper (8.5 and above get a nice looking metal insert) and just looks as though they are punishing the submitter for the lower grade card.
Pros: They have an amazing registry program that has many many many members building their sets under such programs. What does this all mean? it means that if you have a high grade old card of even some scrub, you're going to find a nice payday for it. the set collectors are known for driving up the price for what is known as a "low pop(as in population)" PSA Holder. its been known to turn a $1 common into a $300 PSA Slab. PSA also has a stronghold on cards from post WWII to 1980
Cons: Really flimsy Case. The case is pretty fragile. Dropping one is pretty much a crap shoot if it will break or not (so dont drop them! lol)
Pros: Hands down the best customer service out there. MEGA user friendly. Their Slabs take a bit of getting used to, but i am a fan. They have the market for pre-WWII cards.
Cons: The demand for modern SGC cards is luke-warm at best (great for collectors, but not for sellers)
Sets with black borders (ie.1971 Topps Baseball) tent to suffer eye-appeal wise in a SGC Slab, due to the SGC slab being based on a thick black border that houses the cards.
For the most part, given two identical cards placed on a table infront of you, you really wouldnt be able to tell the difference between a BGS 9.0 and a 9.5if the cards were not already graded.
im going to use the most popular modern rookie card for this example. that card is the 1989 Upper Deck Ken Griffey Jr Rookie Card. There is NOTHING rare about this card, im pretty sure that there are literally millions of them out there. Does that mean its not a "good" card to have? absolutely not. it just means that it will not have tremendous value sometime down the line.
a quick look at ebays completed listings show that a BGS 9.0 sells in the mid $40s (and has for a number of years now. when i was doing my own grading research (over 5 years ago) this card was selling in the $50 area, so not bad) and BGS 9.5's are selling for $130ish. (interesting, since when i was researching them 5 years ago, 9.5s were selling closer to the 250ish area, damn that economy i suppose)
Now, just as there is no right or wrong way to collect, everyone has their own way of doing so. Some people only want gold labels (9.5 or better) in their collection, and those people have no problems spending more for what they want (since its a fact that 9.5s sell for more then 9.0s).
When *i* got into slab (slang for graded cards) collecting i didnt (and still dont lol) have the wallet for most of the gold labels and i had to made a decision. Sure i could get the Gold Griffey and be satisfied, or i could go for the 9.0 Griffey and have more funds to pick up other graded rookie cards that i might want in my collection.
thats the jist of how i got into graded rookie card collecting. Hopefully that made some sense to you people out there :)