That only helps with crew quarters, so crew morale. You want to have enough Engineering Spaces so that there won't be too many breakdowns - and if there are some, you will then have enough Maintenance Supplies to fix them. Finally, you want enough fuel to be able to cruise around for a dozen billion kliks or so, especially for Geosurvey ships.
For the first wave of extra-Solar surveys, I design separate Grav/Geo survey ships so the individual ships don't get too big and then a Jump Tender that's also a fuel and supply storage ship, allowing the TG to remain on mission longer. Since the JT needs to be bigger than the other ships in the squadron, this makes sense. Later on, you will have the technology and shipyard sizes to create a multi-purpose survey ships that you can just send off and not worry about.