Joint economic lot size (JELS) models for a purchaser and a vendor prove to be more economical than when their inventory problems are considered separately. The operational cost decreases further, provided the supplies are made in sub-batches. Sub-batches of varying sizes may cause planning and control problems for both the independent and the joint economic lot size purchaser, but supply in sub-batches of uniform size is problem free. In this paper, two cases of JELS models where a single vendor is supplying semifinished products to a buyer are analyzed. The comparative advantage of the uniform sub-batch supply over the staggered alternative is investigated using illustrative examples. From this, a uniform supply model is found to be comparatively more cost-effective and robust.