I am not disagreeing with the info above but will offer a my experiences as another perspective.
My belief is that most pros run the 620’s as they are faster with the max hp on the boats vs the 621’s. The E-TEC HO and the Pro XS are higher HP motors and push the 620’s into the low 60 mph range vs the 621’s which are mid 50 mph with those same outboards. FLW only opened up its HP restriction rules in ~2009 so guys running the 621’s are now able to mount a 300 on the back.
With that I ran 4 or 5 621’s, 2 – 620’s and 1 – 619 during my stint on tour. From my experience I liked the 621 the best but for the events we fished on a yearly basis as they were more trolling and for that I liked the larger boat. I do pack my boat very full so the additional space was always used. I am not in agreement that these hulls are all wave spearing machines. Have I speared waves in my day – absolutely! 95% of the time though it’s when I wasn’t paying attention and driving the conditions I was faced with. I am confident I can take any boat, point the bow into some good waves, cover my eyes and punch the throttle and soak the carped thoroughly…
I have fished several days in the new hull (post 2008) 621 and am absolutely impressed. I also know the 2008 and later 620’s are equally great boats and the hull changes/interior layouts to both made an already very good boat significantly better!
Now to completely convolute the whole picture – when I was done with my tour days, I picked up a used 620T paired with a 150 E-TEC tiller + the merten hydraulic steering. For how I fish now it’s great boat with the wide open layout for my family with the small kids and my two labs.
Either boat will be great for you – you may want to consider a few fringe details to help you decide:
– garage space?
– potential fuel mileage on you tow vehicle (larger boat will weigh more)?
– how much will you fish precisely (rig, jig, backtroll spinners, cast/pitch) vs troll (cranks and spinners) as there is a difference in having more boat to controll and distract from your fishing?
– budget? – obviously the larger boat with bigger motors will increase the cost and this can be significant.
Good luck and I am happy to help you if you have further questions. Either way this is a very fun and exciting decision you get to make!
-ted