I have a 2017 15" (midrange), and am considering upgrading to the 2018 - mostly for the 32 GB, although the 6 cores are an additional attraction. I use a very large Lightroom catalog that routinely eats all my RAM.
As to the portability question, the 15" is already VERY portable. I may be remembering back a long way, but 13" laptops weighed 4-5 lbs, with 15" models coming in at 6-7 lbs, not so long ago. The 15" still feels like a relatively light 13" to me. The 13" may be even more portable, and meets Ultrabook standards, but the 15" is NOT big or heavy.
The 15" feels like a much better deal to me - $1999 (once you upgrade from 8 Gb of RAM, which feels awfully small) seems very expensive for a quad-core machine with Intel integrated graphics. For $300 more, you get the larger screen, a 6-core processor that is actually faster per core as well (its boost is higher, and it is much less power restricted), and discrete graphics.
It's cheap of Apple to put that undesirable 256 GB SSD in both of these expensive machines - that's an extra $200 to get a reasonable 512 GB SSD. They should eat the extra cost to them (probably 50 bucks or less - the retail difference between the two capacities on comparable PCIe drives is about $80, although it's hard to find exactly the same drive in both capacities).
I'd even go to the terabyte drive as standard on the higher-end ($2799) 15" model, although that's over $150 (retail) in difference from 512 GB, meaning it probably costs Apple closer to $100.
As to the portability question, the 15" is already VERY portable. I may be remembering back a long way, but 13" laptops weighed 4-5 lbs, with 15" models coming in at 6-7 lbs, not so long ago. The 15" still feels like a relatively light 13" to me. The 13" may be even more portable, and meets Ultrabook standards, but the 15" is NOT big or heavy.
The 15" feels like a much better deal to me - $1999 (once you upgrade from 8 Gb of RAM, which feels awfully small) seems very expensive for a quad-core machine with Intel integrated graphics. For $300 more, you get the larger screen, a 6-core processor that is actually faster per core as well (its boost is higher, and it is much less power restricted), and discrete graphics.
It's cheap of Apple to put that undesirable 256 GB SSD in both of these expensive machines - that's an extra $200 to get a reasonable 512 GB SSD. They should eat the extra cost to them (probably 50 bucks or less - the retail difference between the two capacities on comparable PCIe drives is about $80, although it's hard to find exactly the same drive in both capacities).
I'd even go to the terabyte drive as standard on the higher-end ($2799) 15" model, although that's over $150 (retail) in difference from 512 GB, meaning it probably costs Apple closer to $100.
