From an internal perspective the VFC scar uses a V2 mechbox and a G36 uses a V3 mechbox. While some people speculate that V2's have a weaker design and may some day break, I believe that a well maintained version 2 mechbox that has been properly assembled will last a very long time if treated appropriately.
The only bonus in my eyes is that after upgrades or maintenance a user can test a V3 mechbox without having to partially reassemble their AEG.
Honestly I think debating which gun is better is pointless so I will contrast the companies instead. Also I'm not going to bother going into detail about each and every little internal part of each companies mechbox compared to the other. I will give you one example:
SRC currently uses cylinder heads that have dual Orings, while VFC uses cylinder heads that have 1 Oring. Take from that what you will.
If you want more specific details you can do your own research.
Here is a little history on both companies.
VFC has been producing airsoft guns for a little while now, they are extremely meticulous about the detail of their products externals and use fairly high quality materials in order to produce a quality product. In the past VFC used to produce their products with plasticy/polycarb like internals and a not so great quality wiring setup, however most users found the quality of these internals to be sufficient, those who did not merely swapped out what they did not like for something that they felt was more durable. VFC has recently been producing producing their recent AEGs with good quality wiring, non plasticy/polycarb like internals and have even moved onto using reinforced 7 or 8mm bushing mechboxes. VFC boasts that their internals are vigorously test and can provided the durability required to run lipo batteries out of the box.
Like VFC, SRC is not a new comer to the airsoft gun market. However only in the last few years has SRC produced anything remotely close to being called a quality item. Since SRC appeared on the airsoft market they have created low cost low quality items hidden behind shoddy metal externals that drew attention away from the atrocity was their quality control. Recently though SRC has appeared to have revamped its line with new generations of many existing models. These 3rd generation guns boast higher quality internals (compared to their previous lack of quality internals) that supposedly support the required durability for lipo battery use right out of the box. They have come a long way from where they began.
"Its only a little bit on fire"