I would wait on the 20700 cells for a few months, and stick with all the components available for building 18650 packs. If you do choose the 20700's, please post pics...
It depends on how many amps you want from the pack, and how small/large the pack must be. The factory ratings for the cells are not necessarily how I would rate them, but here it is: 25R 20A, 30Q 15A, PF 10A, GA 8A? (these cells used only as an example)
If you need a tiny 2P pack to fit your frame, 25R @ 2P would be 40A, and 30Q @ 2P would be 30A (5-Ah and 6-Ah respectively, for the same size of pack)
If you can fit a 3P size of pack, I wouldn't even consider the 25R...the 30Q @ 3P would be 45A at 9-Ah, and the PF would be 30A at 8.7-Ah (2900-mAh per cell?), but...it is cheaper than the 30Q.
If you can fit a 4P size of pack, then you can suddenly get a boost in range with the GA providing 3400-ish mAh per cell. Approximately 32A and 13.6-Ah. The PF would be 40A and 11.6-Ah
Most ebikers like having a 5P pack at a minimum (depending on how far your commute is between charges, at 14S, that would be (14 X 5 =) 70 cells. At 5P the PF would be 50A (more than needed, not necessarily a bad thing, cells wouldn't be stressed or hot at 30A), and 14.5-Ah. The GA would be 40A with 17-Ah of range.
6P? GA would be 48A and 20.4-Ah
There are other cells that I am not familiar with, and there might be a better cell for your application (amps per cell, range in Ah per cell, and cost). Without any further information available to me, I'd say...for 30A and a 4P size of pack, get the PF cell...for 5P or greater, get the GA cell and enjoy all that extra range...
[all numbers quoted here are approximate, don't trust these numbers, do your own homework]