I plan to install 10  395W panels as a 5 Series x 2 Parallel configuration for a 48V system. From computing the MPPT charge controller, the Excel VEMPPT has 2 options: #1. SmartSolar 250/100 and #2. the MPPT RS 450/100.
Base on the comparison below, I did not see much advantage of the MPPT RS 450/100 controller vs. the SmartSolar 250/100, except for being able to connect more panels in series to 450V. Did I miss something for the MPPT RS purpose? Why would one use the MPPTR RS?
Comparison:
Category  #1 SmartSolar  #2 MPPT RS  notes 
Price  $950  $1295  
Size  Small  Large  
Battery  12, 14, 36, 48  48  
Efficiency @48V  .99  .96  
Power @48V  5800  5760 

Voc Min  +5V  120V  #2  120V is way too high for shadowing days 
Vmpp min  +1V  80  
Voc Max  250  450  
Max PV voltage @ min Temp (10C)  241.7  241.7  #2 has more head room 
Min PV Voltage @ max Temp (70C)  157.8V  158.4V  
Max current @MPP min Temp  88.7A  87.3A  #2 MPPT RS tracker current is 18A 
Max current @MPP max Temp  71.8A  70.7A  
PV Array  5S x 2P  5S x 1  per Track (2)  #2 has room to grow 3 more panels 