Subjective to few factors :-

1) Freehold or leasehold. If freehold - old or new, won't matter much.  If leasehold, the new unit will have longer lease to expiry & the old unit will have shorter lease to expiry. The lease may be renewed or not renewed subjected to State's decision but we may not be living that old to witness it, it only matter when it comes to the inheritance to the next generation.

2) Community mentality living at the condo.

Sorry to say almost 85% of the public mentality are retarded level. Only around 10-15% who are serious to know the Strata Title are being run, the rest of the 85~90% are retarded mentality that don't even bother about. If the old condo have a good responsible community with high awareness / education level - go for the old unit.

The new unit, you will not know about the other owners behaviors' until you start moving in. Chances for your to meet 85~90% uncivilized mentality neighbors is very likely. If that happens. The new unit vs old unit with same shitty mentality of community won't make any different to either old or new unit, because eventually the building will arrive at the pitiful state - not properly maintained due to many outstanding collections.