I agree, I really like the second dress. The only thing that would give me pause on that one, is that you can't easily wear a bra. I have a dress like that and because the material is quite thin it can also be hard to wear a bra underneath. If that is going to bother you, maybe go for the first dress. They're both beautiful so you really can't go wrong!
Yes, boob tape or those adhesive creepy silicone things held together in the middle might work! But some are so sheer that you can see even that - and the neckline means they can open pretty deeply when you're moving around.
(I realise in my first post I forgot to say 'can't even wear a strapless bra')
I'm pretty large in that area and I wore one on New Years' Eve with no problem, but it just depends on if you are having all your conservative family at this dinner, you know? No one wants to accidentally flash Great Uncle Frederick or whatever, haha!
I like the first one a bit better. IMO the satin slinky dresses sometimes just look a little cheap (particularly when the fabric is too shiny, which is often the case with satin polyester) and they really need to be accessorized well to not look too much like lingerie. I do think with the right jewelry, shoes, and hairstyle it would look gorgeous though. But they way they are styled and modeled, I definitely think the first dress appears a bit more chic and is my preference!
I'll second that slip dresses also don't take to undergarments well because the fabric tends to be thin and shows everything, and bias cut dresses are designed to cling to your curves, which mean that they are even less forgiving with undergarments than the typical straight cut dress. I wore a silk slip dress as my reception dress and had to use boob tape and wore nudeseamless panties that were still barely visible some of the time. It was fine, but just something worth considering.
I'd also consider the neckline. I have broad shoulders and a muscular build and anything that is straight across at the top (square neckline or strapless tube top style) tends to make me look even wider, so I always prefer v-neck or sweetheart style necklines because I find they are much more flattering on me.
Both dresses are beautiful though and if the store has a good return policy, I would just purchase both, try them on, pick the one you like best, and return the other. They are different enough that your body type alone could make one an obvious winner once you try them on.
I definitely think try them both on if you can. Every dress fits every body a bit differently!
If you cannot try on the exact dress, maybe see if you can go to a local store and try on dresses or tops that have similar features to see how you feel about them. Like try on a top or dress with a square neckline and thick straps and one with a cowl neckline and spaghetti straps, and a dress with a slit and without, and something that is midi length. And white crepe vs silver satin (or similar). I don't even know if stores near you are letting people use fitting rooms yet, but I think you would get some sense of "this looks good on me" or "this isn't flattering."
I have a muscular, athletic but hourglass build (as in I have a distinct waist) and fair skin and if I just bought dresses based on how they looked on the model I'd probably have a closet full of shift dresses that make me look like a box and soft colors that absolutely wash me out. There is no substitute to getting to try something on if you can!