Many friends ask the question, "What is the most cost effective phone plan to take?"
I have done the calculations and SIM-only plans are always cheaper than signing a 2-year contract regardless of usage. The phone subsidies given do not offset the additional amount paid for the entire duration of the contract. You are better off going SIM-only and purchasing a phone from Carousell or a shop.
Starhub and M1 offer the cheapest SIM-only plans without a
contract, depending on your usage. Singtel gives you a better deal if
you commit to a 1-year contract.
The only exception to this is if you are eligible for corporate discounts and the discount is significant enough to bring down the cost to SIM-only price range. In such a situation, it is possible to get a high-end phone at a highly discounted price. If you do not need a high-end phone, I will still recommend getting the hottest phone in the market that has a low upfront cost, with the aim of offloading it on Carousell or a shop. The proceeds can be substantial, which can be used to purchase the phone of your choice with money to spare or offset your monthly bills. iPhones generally have the best return especially during the launch of a new model, or Samsung Galaxy phones if there are significant telco discounts. A few shops have buy prices online which you can use as a rough guide to calculate your return. Be quick though, buy prices drop fast as supply increases.