If the price is 'minimal' to you (it's a subjective thing), get the pressure gauge. In the event of a flat by the side of the road, you'll roll on knowing your tyre is inflated properly - if this isn't important, why the fook are you checking it before you ride? If you need the pump at other times, such as pumping up a mate's tyre before leaving for a ride (as I did recently when I gave a bike to a nephew and the rotten thing rewarded me with a flat tyre), it's nice to know you've got the tyre to the right pressure.
But realistically, it's a subjective thing. If you're happy riding on something that 'feels hard', do so. If the cost involved in knowing what the actual pressure is gives peace of mind, pay it. I wouldn't criticise either choice, but my pump has the pressure gauge.