I dont think it helps much with paypal. If they file a dispute it will auto be in your favor due to intangible goods but they can always charge back through bank or credit card and you are not even allowed to defend yourself in that situation. I would say paypal does not even fight those in the least, simply charge back your account. It would require man hours and them actually doing something for the seller.
I am actually 100% sure they do not even try to fight for you because after I lost $2400 once due to someone charging back through bank a few months later I had a guy purchase some servers which I was reselling. The sale was good, all maxmind and manual verification checked out. SO I went the extra step and made a form for him to sign and scan, and then fax along with his id. Basically it said he would receive his products, declined management servers and was responsible for his own management, that we made no guarantee on server uptime, just network uplink. And threw in some other things to protect ourselves. This guy had a business web site and personal blog, everything. And was willing to do all this and understood.
TO make a long story short after 2 months he charged back through his credit card service claiming fraud of all things. We uploaded all documents, recorded phone calls, photo id, emails with full headers. Phone bill logs showing the amount and duration of calls.
Paypal did nothing, about 2 weeks later I got to looking on WHT and about 3 other hosts got duped the same way, some much worse. Paypal would not let us in on the arbitration process or anything, said they would handle it.
Now either credit card companies really let their people do this and get away with it multiple times or the latter is likely, paypal did nothing to fight. Probably did not pass along anything to the cc company.
A lot of server companies make you send ids and similar forms and such which a lot of them have the money and legal team to actually sue so unless you have a legal team or money to sue someone when you might not get anything then not much you can do.
I quit server reselling after that, was waaaay too risky for me. I continued doing ddos protection as the majority was legit clients and mainly I just accepted western union for those.
That is one thing you can do though if its a big sale and you stand to have a big loss is simply have them send WU. No way they can charge that back whether they used credit card or not.