The hard acrylic skeleton moulds are typically indicated for those with mild-moderate hearing loss (not sure if that helps you decide)
FWIW, I've had both - I started with the skeleton moulds because that is what my audie recommended it for my type of HL (and I didn't know that all I needed to do was ASK for a silicone instead)...
Personally I find the silicone moulds MUCH more comfortable and that they have much less feedback issues.
With the skeleton moulds, because they are acrylic (hard plastic) they tend to have more feedback issues (even with a large vent). Also if you sweat or it's hot/humid the skeleton moulds "slip" in your ear and can rub sores in the canal or parts of the outer ear which can be very painful. When eating or moving your jaw a lot (ie opening wide like yawning, or at the dentist etc) the acrylic skeleton moulds can't compress at all ... so you often get either feedback/ sound issues, or the mould "slips" when you move your jaw (even if the mould goes deeper into the canal that "typical").
The last time I got new moulds, I got 2 , a silicone and an acrylic skeleton... I THOUGHT I'd use both types all the time, but it's been 2years and I STILL haven't even taken the acrylic skeleton mould out of the bag it came in because the silicone is SO much better and more comfortable.
IF you do decide to try the acrylic mould and get the larger vent, make sure that you book an appointment to have your HA re-adjusted when you go to pick up the mould as the mould material and size of the vent (hole) changes that quality and the volume of the sound ... so you need to have that adjusted. Personally I really prefer the comfort AND sound of the silicone moulds - by a LOT.
(If you order the acrylic instead of the silicone mould, I'd make sure that your audie has the mould company send your impression(s) back - so that if the acrylic doesn't work for you/in case you want to order a silicone you don't have to pay the impression fee again)
Hope that helps
If it were me, I'd stay with the silicone unless you had a really important reason to switch