How far down in SOC will the two 31s get before the morning recharge session? While they will accept big amps at first if down 50%, if they are only down to 75%, there is no point getting a big amp charger. Your existing converter would do as well as any other in that case.
A "50-90" on a 210AH bank starting at 50% SOC using a 70 amp charger set to 14.6ish will take 1/2 hour to reach 65% SOC, then amps will taper for another 1/2 hour to reach 80% SOC. From there it takes another hour to do the 80-90 so expect to be at about 85% at your 90 minute limit.
Of your three choices only the PD can be expected to do that, by using the CW to keep it in "Boost". The other two will drop to 14.2 or 13.6 after the first half hour.
Your other option is to get the adjustable voltage version of the PowerMax. With that you can hold 14.8 (or any other voltage you would need) for as long as you like.