I have a few investment properties and I manage them myself. I have been in a very similar situation to you. I had several families applying and one single man with a dog who wanted the garage for a boat and storage. It was a mistake. He was late with rent on several occasions and we had to send him several notices to remedy. After the third one we evicted him. He released the bond to us but we were still a few hundred dollars short. We went through the tribunal and he has been ordered to pay us the outsanding rent but one year later we are still waiting... We found out later that there were four people in the house.
Your choice should definitely be a business one - take all emotions out of it. You want someone to pay the rent on time (being late is not an option, you should never have to chase it up), someone who will take care of the house and gardens and someone who will stay long term.
The most important thing to me is references from Real Estate Agents. Make sure they are legit - Google the REA's name and call their office not their mobile. Private rental references are risky - they can be anyone (ie. the applicant's friend).
Option A - work out their servicibility - how much money will they have left to live after they pay rent. This will give you an idea if $300 is a lot of money to them. But you'd be suprised how frugal people can be sometimes. If they get Centrelink payments, rent can be direct debited from their payment (they can stop this at anytime). What does their frontyard look like at the moment? They will probably stay around because they won't be able to find anywhere else. I think they will be good tenants - they have more to loose than option B, a house for their child and their reputation.
Option B - Google his name and check him out on Facebook... I wish I had done this a year ago. According to Google my tenant was a bit of a gambler. Feel free to send me a private message with his name - he sounds very similar to my previous tenant! I don't think this tenant will have time to maintain the garden and I would be worried about him moving in with a few friends. He can easily find another house to rent so he doesn't have much to loose if he breaches the tenancy agreement.
In saying all of this I'm not sure if you should take my advice because I've made heaps of mistakes..lol..