There’s pros and cons to both for me I love the comfort of softer silicone they’re less prone to making my ears sore or slowly inching our of my ear I’d I chew or eat or talk a lot. Downside In the past I’ve often had allergic reactions or sensitivity to certain makers moulds. Also I find soft silicone makes my ears sweat terribly which can lead to ear infections or swimmers ear. They definately don’t last as long as acrylic moulds.
I love that acrylic/skeleton moulds tend to have a better fit overall, they don’t stain as easily from wax. Downside is they aren’t as flexible I often find if I’m sweaty or chew chewy foods they have been known to slide out gradually. If they’re poorly for due to impressions that can make my ears sore if I do full Skelton ones.
Currently have 1/2 ear canal acrylic moulds and I actually prefer the style after a lifetime of full moulds but they always needed a little canal hook to hold them in place my current ones don’t have that but they’re still pretty secure
My absalute favourite NHS mould was something called vario therm I think. It was recommended after years of issues with both acrylic and silicone moulds. Starts off hard at room temperature then softens with body temperature so the outer part moves a bit more like a cross between silicone and acrylic. Amazing moulds but I had to fight tooth and nail to get a newer NHS audiologist to authorize making them when I moved away from my NHS audiologist of 15 years. She was adamant I go to the cheapest option I point blank refused and said no these prevent ongoing ear infections, I never have soreness, they don’t need replacing every 6 months or so I never get ear infections with these or reactions like I did to the so called hypoallergenic ones. My ears would be red raw or blistering they spent a few years trying different moulds before those ones and I do NOT want to have to start over again because you think it’s too expensive. That one conceded My 4th NHS audio after another move absalutely refused to do the variotherm moulds again due to Costs, she was adamant they could not get the authorization alas I ended up with repeat ear infections and reactions from silicone moulds and gave up asking. Then moved abroad. I should ask Costcos if they do a similar mould as I’d love to go back to that material.
I wish you luck!