I think you can start with how much is your budget. 
From there you have a list of cars within your budget.  Base on that, base on what you need (eg. family of how many ppl, use for what purpose, maintenance affordability etc), you can shortlist or cross out which one not fit.

If Alza (1.5) vs Persona (1.6) only...
1. Space - Alza definitely win.

2. Power - Persona has more power, but alza has better proven engine.

3. Safety - Persona has better 'chasis' and features.

4. Comfort - depends.. some said Persona better in noise insulation, some said Alza has comfort overall due to space avail.
Maybe relook at your budget, possible few more choices based on your requirement.

Alza S 1.5 vs Myvi 1.5 which one to take as same price