Having your own security system within your own house is easy...but you should see the whole picture.
Firstly, with G&G, especially the more proper type, you will be enjoying the neighbourhood rather than just your house. In other words,, you will be more comfortable to go around the neighbourhood, be it exercise or family activities....given a choice I dont need those grill, this alarms and that alarms, this lock and that lock, etc.....So, in other word, this involve a bit of lifestyle....
Secondly, when you have intention to stay in a G&G, you would most like choose a project that from day 1 has G&G, then most other buyers would be like you, more willing to pay or at least mentally prepare to pay the security. This would be much better comapre with those that need to get consent around....
Of course, there is no guarantee that G&G is safer tha Guarded type, but, the reality is in general, it is better, especially if you have those facilities like guard house, proper fencing, camera, CCTV, and most important sufficient guards....
So, this is the actual reason why there people willing to pick TTDI Alam Impian over I&P. I&P at this point of time, offer more valuable product (house), just comparing the house alone.

However, TTDI has the overall package....that might have a different catchment market..
Have been staying in a G & G with 400 neighbours for more than 4 yrs, love the concept as there is no break in incident in the last 4 yrs. Of course, we need an active RA and cooperation of owner to ensure security guard perform up to the expectation. The guard have to get the owner permission before allowing visitor to access into the compound. Hence, there is no surprise or alien visitor to your hse. However, I really miss the old newspaper van ....
One of my friend loss his brand new CRV two days ago in his Puchong house, the thief drove away the car at 5.30am from his car pouch by de-active the car alarm and opened the so call auto gate!!! The same house was broke in two yrs ago! What's nightmare.