4.2v at 350ma is about equivalent to 400ma at 3.7v (RMS/nominal voltage of li-ion poly batteries) in total charge movement. Li-ion poly batteries charge at nearly 99% efficiency at 1/10C-1/4C charge rates, which these are charging at.

Therefore, the 1500mAh battery should charge in about 3.75 hours, and the 3000mAh should charge in about 7.5 hours, assuming they are both properly rated for total capacity and charge from the cutoff voltage (empty) to full charge with no trickle-rate top-off, as well as an exact 350mA 4.2V charge rate.