It'll depend on if you are able to monitor your bun that evening and night following the spay, and if you feel comfortable doing the after care. It's mostly making sure to keep your rabbit warm(they can get hypothermic following anesthesia, and a cold rabbit is less inclined to want to eat), making sure your rabbit doesn't mess with or chew at the incision site, and encourage your bun to start eating. Admittedly it can be a bit stressful until they get eating again, and making sure they don't try and chew at their incision. Basically you have to sleep next to their pen and check on them all night. I usually set up a small recovery pen next to the couch, for me to sleep and monitor them through the night.
The problem with leaving them at the vet office that night after surgery, is being in an unfamiliar place can overly stress some rabbits and affect their recovery. Especially if they aren't in an isolated room away from the cats and dogs, who will be very noisy and could be frightening to a rabbit. The stress can sometimes be enough to further complicate things and cause GI stasis to set in.
If possible, I would be inclined to bring bun home at least for that first night. Then if by the next day your bun still hasn't started eating and you have to start syringe feeds, those can be difficult to do if you don't have experience with it, so that would be the time to consider possibly boarding, maybe even just during the day so they can help get your bun eating and you could pick back up that night before they close. But if you go with boarding at the vet office overnight, only do it if they have someone there overnight to keep an eye on your bun and give syringe feeds through the night, otherwise there's really no point in keeping your rabbit in a stressful place with no overnight monitoring.
Best is to keep your bun at home if you can handle the care involved. Next best for overnight care, would be to pay the extra for the vet to take your bun home.
http://www.bio.miami.edu/hare/opcare.html