Hi Dan
I have a buddy that bought my D-115 Mk2 to replace his D-90. It really took him a while to decide which one HE liked better. After rolling some of the inputs on the D-115, he finally sold the D-90 but still felt it better in some respects, sweeter mids. The d-115 does have more powerful bass. All things said, I like the d-115 but it is a preference thing. At the same price I would go with the d-115, feeling it offers better value. If you have the chance to listen to both, don't turn down the opportunity. You may opt for the 90.
I have a buddy that bought my D-115 Mk2 to replace his D-90. It really took him a while to decide which one HE liked better. After rolling some of the inputs on the D-115, he finally sold the D-90 but still felt it better in some respects, sweeter mids. The d-115 does have more powerful bass. All things said, I like the d-115 but it is a preference thing. At the same price I would go with the d-115, feeling it offers better value. If you have the chance to listen to both, don't turn down the opportunity. You may opt for the 90.