My impression is that 10 marla appreciates faster even in DHA because of a number of factors. I don't like to buy 10 marla in DHA because price is too close to 1 kanal but that factor itself shows that price increases better than 1 kanal.
Reasons are firstly the 20-25 lakhs difference in price means the buyer pool is significantly larger.
Secondly, it is less expensive to construct. Thirdly, there are too many potential tenants for 10 marla as compared to 1 kanal and rental difference is not much. In one kanal if you construct 2 units, you have to deal with 2 tenants - each of them paying much less than the single 10 marla tenant.
You asked about DHA-3, that is a good option but location wise, DHA-2 is much better so there is a difference in potential.
As for 5-kanal ROS, one would think it has a lower potential for growth but so far the results are not bad at all. Files in late 2012 at 45 lakhs became plots in mid to late 2014 and prices rose to 65-90 lakhs depending on location. Since then prices are stagnant because the file-to-plot conversion factor has been utlized by initial investors. So some people after taking this cream tried to exit further depressing the prices.
However, my gut feeling is that at current prices, a fully developed 5 kanal plot in Multi standard development plus facilities is way too cheap. Bound to go up. But all said and done, it is safer to go to ROS with a mixed objective: Price appreciation and Personal living. Dont go there only for price appreciation.