Hi, some of my opinions for your consideration:

I've owned a Persona HL for the past 2 months.
So far I've no major issues, the minor issues are:
i. some minor rattling sound from the plastic dashboard.
ii. some plastic defects which Proton has agreed to warranty and replace for me.
iii. Slightly high FC, not much of an impact to me compared to my Manual Kancil since I'm doing average mileage a month (~250km per week). If you're doing >1000km per week defintely you need a Vios or City IDSL else the petrol cost is enough to balance up the monthly loan payment.

1. How much would both cars cost you in terms of monthly payments? Check if both is within your budget, else the choice is obvious; go for what you can afford.
I'm earning >RM4K a month but with the fact that I'm also paying for my home and getting married + putting away 10% for personal savings I can only afford the Persona.

2. Are you a fresh graduate or are you looking for a family car?
- If you're looking for a family car go for the Persona (bigger boot and rear seat space, I've sat in both before). The low torque at low rpm is not a problem since I'm not planning to race on the roads and don't frequent the highways.
- If you're a fresh graduate/ beggining to climb the corporate ladder, the better choice would be the Vios for better FC and styling. Also this may help to attract girls (*8/10 of my girl friends aged 18-24 gives full thumbs up for the Vios for style).

3. If you decide to buy the Vios check that the service booklet and make sure it has a good service history. Else since it's your relative why not bring to Toyota service for an assessment?

And most importantly, whichever choice you make enjoy your new ride.