There are very few phones with DSDA option, especially among the well known brands. Whether or not it is going to influence your decision, depends on your usage. If you have given out both your mobile numbers to everyone and want to be always reachable, a DSDA would be better, but your options are very very limited.
Yep, that's right. Dual Active phones are a rare breed and most of them are either cheap Chinese branded phones or mid rangers. I personally never understood why a higher end dual sim phones which are themselves a rare breed cannot have a Dual active capability.