That said, I have used Nexguard and Bravecto on my seizure having lab and have no issues.
We've used a lot of Nexguard in our rescue too -- and we're dealing with dogs without any known vet history, often in terrible shape. We tend to have more than our share of crazy side-effects on a huge range of drugs pop up simply because of the population we're vetting, and the lack of a history.
When dogs show up covered with ticks, it's so important for us to use something effective that will get all of them, even hard-to-find tiny ones in little nooks and crannies that even careful exams can miss. Nexguard has been really helpful for those dogs. It's also been wonderful for off-label use treating bad
demodex in HW+ dogs (where high-dose ivermectin isn't possible).
We've also used Bravecto to a lesser degree. We haven't had side effects from it either, but we have a smaller sample size to compare.
It's worth remembering that Trifexis/Comfortis also has seizure/adverse event reports. We've had whole threads about the weirdness of the unpredictability of which ones react to that product.
Frontline has other issues -- the EPA classified it as Group C (possible human carcinogen) based on rat studies finding increased thyroid tumors (though my recollection is that the rats were fed fipronil at high doses). I also have a vague recollection of some osteosarcoma correlation too, but I can't put my hands on the research right now and might be mis-remembering. Here's the official Fipronil info:
Fipronil Technical Fact Sheet
Ticks transmit awful diseases that can kill dogs, or destroy quality of life. Tick diseases aren't always easy to treat. Fleas aren't just annoying -- an infestation can suck enough blood to make a dog anemic, and even kill puppies (and even mild cases can still transmit other parasites or trigger allergic reactions that are absolutely miserable). For those in warm climates where EOs just aren't enough protection against really voracious bugs, not using parasite prevention has its own dangers too. So please try to keep a balanced perspective and talk with your vet about your dog's history, your environmental concerns, and the disease profiles in your area, to make good, evidence-based decisions for your individual dog!