i personally prefere the b-series, but then i prefer older cars to new ones. the b-series are extremely good engines , with the b16b (out of ek9 type-r) producing 185bhp, which makes it one of the worlds most powerful production normally aspirated 1.6! the k-series are better though on paper, they are more advanced, have better parts/design and a more advanced i-vtec. a b-series like the B16A2, or even the B18C1 would be much easier to put in a del sol. the crx del dol si-r came with the B16A2 out of the factory so would have no trouble going in. putting in a k-series, such as the K20A would require more engine mount work, and modification.