You couldn't tell the difference between a '918 and a '4148... the 4148 I think has a higher forward current capacity and the '918 has a few uA less reverse leakage as well as a slightly higher switching speed but the differences are small, Use the 1N4148 as the 1N9XX diodes are really no longer even Mfd'd. I've attached data sheets for both in case you are curious.
Bob
1N914.pdf (141 KB)
1N4148.pdf (62.1 KB)