If it's a choice of keeping them in containers vs. putting them in the ground ... I'd say put them in the ground. Good layer of mulch, keep them watered and they'll be better off.

There is a big difference between actual "Transplanting", which means digging something up, stressing, and disturbing the root system : or just planting something that's potted, that really will grow better in the the ground. In the ground, it doesn't need to be watered as often (except at first, be careful not to over water either), if the soil is properly prepared and mulched. It will be able to establish more of a healthy root system. One way to decide, is to pop one out of it's pot and see what's going with the roots. If they are bound, they definately need to be planted, if not wait til later when the growing conditions are more favorable to new plantings.