The Shield is a lot bigger than the P290.
The Shield is 4&1/2 inches in height vs 3.9 (P290)
The Shield is longer with a overall length of 6.1 vs 5.5 (P290)
The width of the shield is .95 inches vs .9 (p290)
The Shield is small but definitely not nearly as small so not really a valid comparison.
The Nano is 4.17 in height
Overall length of 5.63
and width .90
It and the P290 seem to be a lot more equals...