Chloride enhances malt flavor. Gypsum/sulfate enhances hop bitterness. If you prefer one over the other for a particular style then decide based on that. If you want a balanced beer then use them 50/50 or lean a little more towards chloride as calcium chloride is smoother and less "offensive". If you use a lot of gypsum the beer will taste harshly bitter. Too much chloride? Meh... almost impossible to do that. A calculator like BrunWater is still your best bet if/when you are ready to get serious about water adjustments, which can be put off for later.
^^^^ Exactly. I start my recipies with a 50/50 split and that works well for the beers I like to drink. It works for my hoppy American Brown Ales... right on through to my German Pilsners. Even the Belgian APAs and Porters come out great.
If I have a beer that I want the hops to pop a bit more, or make the malt pop more, I would shift the ratio so that I use more Gypsum to make the hops stand out, or more Calcium Chloride to accentuate the malt. (Note, I have not found a reason to do this yet)
My homes have traditionally had hard well water, and that is what I used quite a bit in my brewing career... the wisdom I have learned is that less is more when it comes to minerals in the water. By going distilled/RO it gets the minerals "out of the way" and with a simple addition of putting back a few minerals to the water...everything becomes consistent and easy... and the flavors become less muddled and stand out on their own.