You don't get any feedback on the percentage of enlargement or reduction in Safari, and you do have to do it for every visit, and every site that opens in a new window or tab.
However, you can create your own custom stylesheet to set a default zoom level for each page, regardless of anything else.
1. Create a file named defaultzoom.css (or any name you choose, as long as you save it with a .css file extension.)
2. Copy and paste the following:
body {
zoom: 150%;
}
*(Note: This 150% value is used as an example only; you should enter the value you want to use.)*
3. Save the file to Home/Library/Safari, then open Safari's Preferences > Advanced section. In the dropdown menu where it says "Style sheet:", click it and navigate to the style sheet you just created and choose it, then close the Preferences window.
4. Quit Safari and restart it, then browse the web as usual, with your new default zoom setting. If you want to change the amount of zoom at any time, open the style sheet and change the value, save it, then refresh the page(s) in Safari.