Personality
Any fan of the series knows what Goku's like so I wont talk specifically on about him but I will mention him in comparison to Black.
Personality wise they are almost the exact opposite from each other. Unlike the simple minded and down to earth Goku, Black seems to have a much wider view of the world. While Goku understand right and wrong (in his own way) Black seems to actual understand the concept of justice and of how his actions effect the universe, something Goku doesn't really give much thought to. Black also has a broader mindset then Goku, for example he seems to takes pleasure from the beauty of things (roses and his SSR form) and appears to be somewhat poetic, something Goku has never displayed. He is also sadistic, as he enjoys the act of killing and causing pain, while Goku has at most only ever taken satisfaction from doing a similar act to others who have hurt or killed his friends and family. Black also displays masochism i.e. taking gratification from one's own pain as he is seen to often be smiling while receiving attacks. This is another aspect that Goku doesn't display, well no more then any normal fighter would. Goku is for the most part a very moral person (in his own way) while Black is very amoral and dose whatever is necessary to achieve his goal. Black displays a "black" sense of humour as well as often talking to others condescendingly. Both do display a great deal of stubbornness and determination. They are both very confident in their abilities but while Goku can be overconfident on occasion, Black displays true arrogance. While Goku can be thoughtless and selfish at times, he's a saint compared to Black.
However its clear that they do share the same passion for fighting. Black also displays Goku's ability to quickly learn and adapt while fighting. In-fact he may even be superior to Goku in this regard as he was able to copy Goku's fighting style after having fought him just once. Like Goku, Black prefers not to go all out at the start of a fight to try and prolong his enjoyment of it (although as stated above his reasons for doing so are very different).
Black's entire manor and way of speaking (as far as I can tell) is far more formal and serious then Goku's.
Fighting Style
I have always seen Goku as primarily a melee fighter who specialises in a good balance of defensive and offensive ability. In regards to ki, Goku actually has a very smaller pool of attacks when compared to the most of the cast, best example being that he has only one "normal" signature attack, the kamehameha and nothing else while every other characters will have several attacks that they use. Goku really has no other moves in this category and his other move pools are like wise very singular. Kaio-ken to boost his power (dropped after gaining ss forms until Blue), Instant Transmission for travel and speed, Taiyōken to stun foes and the Spirit Bomb as his final ultimate attack. He has also used the Kienzan but only when he has needed to. However rather then coming up with new attacks all the time Goku has adapted his small pool of skills to a very wide range of situations. Goku also rarly resorts to spamming ki blasts as much as other characters. Goku also doesn't seem to be quite as good at ki control as other characters. While he has learned some ki shapeing skills such as barriers and the Kienzan he doesn't appear to be very good at remote controlling ki blast like Vegeta, Piccolo, Kuririn and even Yamcha. The best he has done was bending his kamehameha and when fighting Frieza, where he held two ki blasts inplace and then firing them up. A lot of this is likely based around how his original training with Master Roshi and his grandfather shaped his personal preferences as a fighter. On the flip side Goku has amazing ki sensing abilities, often out shining most of the caste in this regard. Goku also holds back on using other peoples attacks because he views it as stealing. Goku also often holds back from using all his skills at the start of a fight and will often come up with new tricks on the fly.
Black's fighting style appears to be more offensively based then Goku's and while his defence his very solid he seem let his guard down on purpose, possibly due to his masochistic nature. Although he seems to only do this intentionally against weaker fighters. Black makes far greater use of ki attacks then Goku, often starting his attacks by firing ki blasts and makes far more use of ki barrages. Like Goku he makes regular use of his Black Kamehameha as a signature attack. Black's use of a very focused ki blade displays a high level of ki shaping control and compliments his more aggressive style. Like Goku, Black is not one to play all his cards at the start of a fight however he more then willing to use lethal force and attacks. While Black dose hold back so he can enjoy his fights and sometimes intentional lets his guard down unlike other villains he dose not seem to be one to toy with his opponents and takes all his fights seriously. Black dose have access to Instant Transmission but has yet to make any use of it in combat and is stated have only learned to sense ki very recently meaning he may still suffer from some of the problems Vegeta ran into on Namek. Also unlike Goku, until Super Saiyan Rose, Black did not make any use of transformations or power up techniques (as far as we know) implying his base form power is incredibly high. Black also displays an incredible aptitude for development and growth as a fighter that may even significantly surpass Goku's.
Well that how I view the two at the moment anyway.
