I’d say it’s the first rather than the second—something like “on both counts,” referring first to its sheer fabulousness and then to the specially disagreeable quality of fulsome praise, each intrinsic to the genre and vitiating its enjoyability. But it’s a long time since I read this.
Thanks for your thoughts, I agree, the ‘correspondance/alternating’ use of παρά here (LSJ C III 9) seems a bit of a stretch when used with ἑκάτερον. I’m not even sure it makes logical sense.