While it is arguably true that in the past, eBay/PayPal always/almost always allow the buyers to win in any/most PayPal disputes they open, these days eBay sellers have a bit more protection from scammers, assuming they meet the requirements for the "Seller Protection Policy".
Whether you will succeed in your "Item significantly not as described" claim remains to be seen. In any case, the correct procedure would be to:
1) Open a PayPal Dispute.
2) If the above was unsatisfactory, then the PayPal Dispute can be escalated to a PayPal Claim.
PayPal User Agreement wrote:13.4 Dispute Resolution. If you are unable to resolve the problem directly with the Seller, go to the Resolution Center and follow this process:
Open a Dispute. Open a Dispute within 45 days of the date you made the payment for the item you would like to dispute.
Escalate the Dispute to a Claim. If you and the Seller are unable to come to an agreement, escalate the Dispute to a Claim within 20 days after opening the dispute.
Under a PayPal Claim, PayPal themselves will investigate the transaction and any decision they make (siding with the buyer or siding with the seller) is final. Generally, you would want to make a PayPal claim if you know you're going to win because you know the seller stuffed up somewhere. Under a PayPal dispute, the buyer and seller merely communicate to find a mutual agreement without any communication from PayPal.
3) As mentioned in earlier posts, if payment was made using a credit card, the 3rd option is to initiate a chargeback (60-90 days), getting your money back by bypassing PayPal entirely.
When a transaction goes wrong and a PayPal Dispute/Claim is made, PayPal does not take any risk. If a scammer buyer wins, then they keep the item and money (and the seller loses). If a scammer seller wins, they also keep the item and money (and the buyer loses). PayPal won't lose anything and may or may not win (from the fees) so they are generally indifferent to both situations.
When a credit card chargeback is made (a fee applies), it is possible for both the buyer and seller to keep their money, while PayPal is forced to take a loss if they can't retrieve funds from the seller because it has already been withdrawn or because the seller followed all policies correctly.
My concern is that, since the buyer went through a non-PayPal channel, PayPal will decide to suspend the buyer's account in order to mitigate any possible future losses from this particular account (i.e. PayPal doesn't like chargebacks).
I do not have enough information to know how likely this is to happen and I'm not sure whether different rules apply to different people (e.g. a casual buyer who does a credit chargeback twice will be suspended while a PayPal account that deals in many transactions may be left alone since it's still an asset for eBay/PayPal despite the losses from chargeback).
Just something to consider if you care (and you should) about the benefits of having a PayPal account.