Manulife Shelter VHIS Standard Plan is the insurer's Standard VHIS plan (the regulatory floor of cover), while Manulife Supreme Lite VHIS Supplementary Benefit - Smart is its flagship Flexi plan, which extends the ward class, benefit limits and geographical coverage above that floor.
Manulife Shelter VHIS Standard Plan suits you better if you value a lower entry premium (about HK$2,481/yr at age 40, non-smoker). Manulife Supreme Lite VHIS Supplementary Benefit - Smart suits you better if you value a higher annual benefit limit (HK$4,906,250) and a stated lifetime benefit cap (HK$19,625,000).
Neither plan is categorically better — your choice should rest on your own budget, where you expect to seek treatment and your family needs, ideally after a financial needs analysis.