SW is a real good game and way better than DK IMHO. I enjoy both but SW is more realistic with weapons and fights. Nobunaga is way more bad ass in that game. In fact one of the only things DK has over SW imo is a cooler looking Date with a better moveset. Date's musou move in SW isn't really good. Between the three games here is how I break down each Date.
SW
He is a very young badass who whoops ass. His moveset is alright but his musou isn't that good especially when compared to his DK or SW2. All you do in this one is fight two armies at once instead of choosing an ally like his retainers humorly suggest.
SW2 kind of ruined him but still made him good in a way. In this one he grows up but loses some of his bad assness. Instead of jumping in the middle of a battle between two armies, he turned into a lapdog who was loyal and ready to serve whoever had the most power throughout the entire game until the end where he turns on Ieyasu. His moveset is way better and its my favorite of the three, and he uses pistols as well as a sword but the fact that he turned into a servant was a huge let down.
His DK version as you know is absolutely badass, older, looks cooler and is able to wield 6 swords. You already know about him so there is no need to continue.