The new version of Apple’s tablet delivers 3G connectivity, but there are trade-offs. Apple’s newest iPad, the 3G-equipped model that arrived Friday, is identical to the earlier Wi-Fi-only model, save for a plastic black strip running along the top of the device — for 3G reception — and a SIM card slot on the lower left side. Otherwise, the iPad 3G offers the same features as the model that arrived April 3: same solid design and construction, same bright and sharp 9.7-inch screen, same battery life.