Can't tell if you're trolling or really that clueless.
Just in case you aren't trolling, the youtube video you showed is pointless. Using two different systems, with different specs isn't a reasonable comparison of Iris vs. Iris Pro. if you're serious about understanding why you're so wrong, check out benchmarks for Iris vs. Pro (Anandtech is a good place to start). Common benchmarks show that Iris Pro is SIGNIFICANTLY better than Iris,
http://www.videocardbenchmark.net/compare.php?cmp[]=2692&cmp[]=2562
It's not close.
To sum things up:
1. No, the base model 15 doesn't have a dGPU.
2. No, the base 15 doesn't have any issues with windows and battery life.
3. Yes, the 15 quad core is significantly more powerful than the dual core in the 13, and it's readily noticeable.
4. Yes, the Iris pro graphics in the 15 are significantly better than the Iris in the 13.
You're wrong on just about every piece of advice you have given out. Please stop.