PS3 works great on the vast majority of content (i.e. where there aren't a gazillion players all crowding the same spot). Most of the time, its performance is nearly indistinguishable from PS4. It does however take just slightly longer to load the presence of mobs and players, and sometimes in crowded situations this leads to there simply being too many for it to handle properly. (Though it sounds as though your current system has this problem even worse.)

As far as PS3 being "the worst ever!!!!" no. It's worse than a high end gaming rig with all the latest and fastest components. And it's worse than the PS4 version. But it may be a middle ground between what you have and what you'd ideally want.

I'd say go ahead and purchase the PS3 version. (As mentioned, hard copies tend to be cheap now. And you do get a month's worth of subscription time with it anyway.) That lets you try it out on the system you already have and see for yourself whether it's enough better to satisfy your needs. If it's still not good enough, then you can look for other alternatives.

Oh, if you do end up borrowing your friend's PS4, be sure not to accidentally link your SE account to your friend's PSN account. You'd need to set yourself up as a second user on his console but with your own PSN account.