I like to speak in points so...
1. Speaking of build quality, how many falls will a phone armed with gorilla glass stand(say from 3-4ft) before it finally breaks?
Tricky question, depends how it falls, face first, side impact or back. Then there is the point of impact which is random. You may survive a face fall and have problems with the back. I don't think any phone is certified to survive a drop. Drop tests are pure entertainment, its not possible to say anything meaningful with a sample size of just one. So people go in for cases, to protect the sides and lips to protect the front. As a side bezel replacement is labour intensive and invariably requires lifting the screen off.
From what i can tell build quality is more to do with how it 'feels' in your hand and your 'impression' how it will survive daily wear & tear. People go on about aluminium shells >> plastic and how nice they look but they scuff & scratch easy and can be expensive or difficult to replace.
What looks or feels good does not necessarily translate into longevity. Plastic wins there hands down.
2. What does it mean when someone says that a phone has poor touch? Is it the consistency? Amount of pressure needed? Accuracy? My theory is that the touch quality shouldn't matter if you are gonna use only one phone for the majority of the time. Once you get used to the touch, you'll know "how much" to touch.
I've been using Nokia 5530's resistive touchscreen for 3+ years now. When i have to use a phone with a capacitive touch, i have to control myself from poking the shit out of the screen. But i believe when i get a capacitive phone, ill get used to it in a week or so.
Its to do with the tier 2 or even tier 3 touchscreens used. Inconsistent touch in certain areas. And this is a real lottery, you might get a model that works very welll or one that does not. tier2 or tier 3 have less rigorous testing or quality standards and are cheaper. Can't buy this online, you need to inspect the product and test it properly before paying. In effect do your own QA. If you are used to buying from the grey market then this is the same. Better be familiar with the service codes of the phone you want to buy so you can run your own test in the shop.
3. If i were to compare mediatek's quad core with snapdragon/qualcomm's dual core, by what margin would the former beat the latter? Is there a noticeable gap?
Depends on what its used for. Stress testing will show its not just the CPU but also the memory and how smoothly the bit shifting ensemble works.
tier-1, is tier1 for all components, except maybe cameras.
tier-2, is potluck for all components with even tier-3 added for more aggressive pricing.
In short you do not know what you are getting. The specs and price may be attractive but the experience is mixed, and even among users of the same devices inconsistent. 3rd party development is also slight to non-existent except for certain models of which its tricky to tell. You get the device for cheaper for a reason, the company only commits to support you for the OS it came with, any further updates are uncertain. Maybe or not.
Given the long service times, it goes without saying you need two phones to be able to ensure that you will have a phone at all times. You need this even with tier-1 but its essential with anything less.