I don’t know much difference between both normal and platinum tip which is slim tip plug, but I can share my experience with you,
I went to Badami Bagh spare parts market to get these platinum tip plugs, Nizami Autos I got 4 of them for Rs 1200 for my Altis Automatic 2006 Model,
After installation I observed smooth start along with minor difference in pick up, fuel consumption was almost same.