They both suck in wet areas. Especially when applied over a dirty surface. If you use either, expect to have to replace it when it’s starts peeling or cracking.
The reason why tile industry standards recommend those types of sealants is because tile corners move or expand and contract which is normal. They shouldn’t move much but any slight movement will cause grout to crack because it’s not flexible.
It is important to keep your shower floor sealed as much as possible to keep water from getting under the tile. There is a waterproof membrane of some sort that keeps that water from getting out of the shower. Depending on the way the shower floor was waterproofed could mean that there is a mortar bed between the waterproofing and tile. This mortar bed can wick that water and cause all kinds of moisture issues like mildew and mold.
You want to keep that shower floor dry between uses to slow down this issue. There are some waterproofing membranes that tile is directly bonded to and this works 100 times better because there isn’t any accumulation of water. The shower does dry out between uses and keeps moisture issues to a minimum. You still want to keep the shower floor perimeter sealed with something.
I prefer to use epoxy grout for corners as it seems to last much longer and I can use any color grout for color matching. Super Grout Additive is my preferred choice as I specifically designed this product and have been using it since 2010. It’s epoxy grout and can be used for new shower floor tile installations which is waterproof itself, or at least as waterproof as tile which is good enough. The amount of water that gets under the tile is so minimal that it dries up between uses. This extends the life of your shower indefinitely.
Mold grows inside caulk and silicone. Chemicals and bleach won’t fix moldy caulk or silicone. You have to remove with a razor scraper, then apply a mold killer before any applying new caulk or silicone. I prefer to use Super Grout Additive epoxy grout for all corner grout repairs.
No chemicals will remove the bulk of this soap scum. It’s a waste of time trying to spray with bleach, acid or alkaline based cleaners, or pressure washers. Razor scrapers and stainless steel brushes used here with a home made cleaning cream. Soft scrub and glass bead media works pretty good using a brush or 3m Scrub Pads
Caulk and showers don’t mix when the shower doesn’t get to dry out between uses. Plan on replacing when the mold starts to set in. There is no option to clean this stuff, you have to remove and apply a mold killer to stop the growth before applying a new bead of caulk. I prefer epoxy grout myself.