Since you've been commuting between CWB and TST over the past few days, what you should have done then was bring one of your bags to the Sheraton luggage room today or yesterday. They would have happily held your bag for your arrival. This would have made the MTR trip tomorrow really smooth. Regardless, you can easily carry those two bags onto the MTR (or even the more convenient bus), but the taxi without a doubt is still the best option. Nothing beats door-to-door service.

Or, you can test the labor market and offer HK$30 plus transport to the first unemploy guy you see on the street and see if they will be your porter for an hour and carry your bags for you on the MTR. By my reckoning, you will save HK$20-HK$840 if you do this