Few other things to consider....if you decide to go for a Neo because it is new and backed by warranty, but you are unhappy with the Campro and end up modding it, you are likely to void the warranty anyway. These days most warranties are drawn up so strictly, anything but the most basic of mods will void it. I would speculate that in order to get your Campro some much needed grunt you may have to engage with mods that void your warranty or put you on a borderline case of voiding it. Best to check with Proton beforehand what can or cannot be done.
If you want my personal opinion, I would go for a GTi. I always thought the Satrias are good looking cars. A Neo looks better but the Satria models are still very nice. A tastefully done up Satria is an attractive car. Looks are one thing, but just like a lot of things in this world, looks will only get you so far. If you want to drive a car because you enjoy driving, I'll go for performance first and, in this regard, a GTi is preferred.
Age of the car is one consideration, but as I said earlier, if you end up modding you void warranties anyway. If you done your homework and got someone who is trustworthy and qualified to make an assessment for you before you buy, you reduce the likelihood of buying a problematic old car. Besides, you don't see any shortage of consumers rushing to buy those warehoused Iswaras that Proton recently released at promotional prices.
To be honest, I would prefer to get a Putra...with the GTi a close second preference. Likely, I wouldn't even consider a Neo. This is just my personal opinion.