Been waiting quite awhile for this comparison, and finally the quarter has ended. It is simply Q1 and Q4 PS4 sales in Japan.
2014- Q1 2017 from Shadow. Everything else is my attempt at the numbers.
Q1 2014: 493,338 (partial quarter; incl. 309k on launch week)
Q4 2014: 244,588
Q1 2015: 378,434
Q4 2015: 456,834
Q1 2016: 382,680
Q4 2016: 797,172
Q1 2017: 512,789
Q4 2017: 651,736
Q1 2018: 719,753
Avg Q1: 497, 398
Avg Q4: 537,582
Conclusions: FFXV and MHW created quite the monster quarters, but otherwise they are fairly equal according to the averages . Holiday boosts seem nonexistent for PS4. However with each Q1 the next Q4 was always better except for launch year. Will Q4 be bigger this year? Obviously depends on games, but it is definitely a possibility.