<p>Just to be clear, 1:1 previews have nothing to do with viewing the image in the Develop module...Preview in Library and Loupe (whether 1:1 or not) is ignored in the Develop modual. In Develop, the original raw image data is loaded directly–regardless of what previews are available. There are a few things that effect Develop module previews such as Fast-Load Data and Smart Previews (not to be confused with any Library Previews).<br>
As far as the relative file size differences between Standard & 1:1 Previews, that's tough to answer because that are different sized Standard previews...but ya gotta figure that 1:1 Previews will be 2-3X the size of Standard Previews.<br>
But, in the grand scheme of things, I don't think preview size should be a deciding factor. HD space is cheap and having 1:1 previews saves time if you need to inspect images at 1:1. If you don't build 1:1 previews in advance, then you'll have to wait for LR to build those previews when you need to see the images that large.<br>
Pick your poison...now or later. If you build 1:1 previews while unattended, then you can navigate through and do selection edits a lot faster.</p>