It's okay, I over think everything as well Better to be well-prepared!

Ghann's has been in the business for a long time and is a trustworthy company from what I've heard through the grapevine. If they make the claim that Gryllodes are better for these reasons, then a noticeable difference may actually exist, given the amount of time Ghann's has been working with each species (and the [presumably] millions of each they've produced). Id say go for it if you are set on breeding crickets... but further advice on that matter will have to be given by someone with more experience in that area

As for an alternative third option...

This time of year is a particularly good time to rear silkworms (Bombyx mori) because mulberry leaves have already started to come in. If you live in an area where mulberry grows, and you know you can harvest plant material safely without fear of any chemical -cides or sprays, silkworms may be a decent option. These guys are notoriously expensive... but a big factor in this cost is the artificial chow requirement. They will only feed on this artificial chow or mulberry leaves, otherwise they will not thrive.

It may be possible to order a small amount of food and eggs periodically (or attempt to breed them, they aren't too difficult). The chow would be needed for the first week or so of life, but once they reached their 2nd instar they should be able to handle mature mulberry leaves, and you could harvest the rest of their feed from outdoors for free. They do require a little maintenance, however. They need to be fed at least once, preferably 2-3x daily. They also excrete quite a bit of frass and some silk waste, but this isn't a big deal with some forward planning (e.g. you can rear them on plastic grating so that frass falls through the holes but larvae and food remain on top).

The benefits of silkworms is they are (arguably) the most nutritious feeder out there. Soft bodied, very high protein to fat ratio, high in calcium, and they contain an enzyme called serrapeptase that is known to reduce inflammation and arterial plaque, and promotes calcium absorption. This makes for a bit of a trade-off: a more expensive, slightly more demanding feeder in exchange for nutritional benefits.

Another possible option might be an additional cockroach species... there are dozens available they make good feeders. However, most roaches have very similar nutrient compositions... so it may be better to go with another type of insect to promote a more varied diet, especially since you already have two species.

Soldier flies (Hermetia illucens) are another option, and I'm told they are quite easy to rear. The larvae are soft-bodied and fairly nutritious, plus very high in calcium (sold under the names "calci-worms", "repti-worms", and "phoenix worms"). If you are into composting, some companies actually sell large soldier fly colonies in special pods meant for composting ( BSF bucket composter v2.1 » Black Soldier Fly Blog and Home Page - BSF Farming ). While I've not done this, it seems pretty easy. The adults are wasp mimics, but are totally harmless and also safe to feed. I would wager blue bottle flies (Calliphora sp.) wouldn't be all that difficult to rear on a artificial or 'safe' diet as well... both larvae and adults could be fed in this case, too... but you'd have to look more into it. I know some mantid keepers feed them and/or rear them.

It's too bad he doesn't like earthworms, those would be perfect for you. Slugs may work and I wouldn't think they'd be all that difficult to culture. I'd imagine you'd just keep them in an enclosure with a substrate that holds some moisture and offer produce for them to feed on. Maybe someone else has more experience with them... I recall at least one thread going into a little detail on slugs if my memory serves me right (try a forum search).