It's quite more favorable to buy things in bulk not only data but every other thing we use on a daily basis. I get value for my money when I buy food items in bulk than when I get in bits. For instance, when you buy rice in let's say a full bag or half bag, it pays you more than buying in 'mudu'.

Back to your question, i use glo data subscription and I opt for the 3k for 14gig (30 days validity period).