rotation: swede - brassica or root ?

After reading few quite books on growing vegetables - they seem to contradict each other. I've been reading about the potatoes - legumes - brassica - roots rotation plan and am now very confused. The reason for this confusion is because some books ie the allotment book & bob flowerdews book suggest to grow swedes with other roots - whereas in the vegetable expert book and on this website they suggest that as swedes are brassicas, they should be put in with the brassicas.  Please could the more experianced veg growers let me know where the best place is to grow swede - either with roots or other brassicas? :?

Like crowndale has said they are brassica's and are subject to the same problems, but IMHO there's no right or wrong way to place, each has it's advantages/disadvantages.