I didn't know they had carboys with spigots. Are you planning on bottling from the carboy or are you going to rack into a bottling bucket for bottling? If your thinking of using the spigot to transfer to the bottling bucket, I think the auto-siphon is the better option. I think you can get a better rack (leave more sediment behind) from a siphon then from a spigot. Down sides to spigot: they need to be cleaned threads and all, they can leak. Down sides to auto-siphon: people tend to break them, have problems with them. Mine works great, haven't had any problems. I'm not sure why other people have reported difficulties.
If it were me I'd probably go with the auto siphon option unless you want to bottle right from the carboy, then I'd go with the spigot.