I used to be a big fan of expanded peat pellets until my local farmer supply changed the brand they carried to one that is wrapped in mesh so thick that the roots just can't penetrate. MY seedlings just sat there doing nothing after I transplanted them and eventually I dumped out one of the pots to find that there was NO root development outside the pellet. Now I just use nursery 6-packs with compost, vermiculite, and sand. If you wait until the seedlings are pretty pot-bound to transplant you should have no problems just yanking the whole mess out.