Each has it's own card features. Visa Signature may give Supp Cards unlimited entries to airport lounge but it earns you less Enrich Miles with every Ringgit spent overseas and locally. So, for those who want Supp cards to enter PPL and do not need the Enrich Miles or Kris Flyer Miles but prefer Treats Points for redeeming cash vouchers or other stuff, and still need a card for overseas (5XTP), better to go with Maybank Visa Signature.

For those who use needs a card for Insurance and Quit Rent and etc where AMEX cannot be used (exclude petrol and groceries), the Visa Infinite 2X TP for local spending 100% better than Visa Signature 1X TP.

The supp card never mentioned that it is a supp card, right?
If yes, just quietly use it and test luck

email from CS in July 2014 confirmed it is allowed.

I did confirm once with Maybank CS and they told me that MBB VS Supp can can enter for free like what Human Nature said. Maybe you should call Maybank CS to reconfirm as sometimes branch people know nuts. Or were you informed by a staff at Maybankard Centre? Those at Maybnkard Centres are more familiar with their credit cards.

Went to the lounge at Gate P international departure hall (Wellness Spa) last week and love the view from the lounge. Took me a while to find it though as the entrance is rather small and sandwiched between 2 big restaurant (Popeye's Chicken and McD if I remember correctly)