Both but i like to keep them as fighter. You can see at 1st page all the exciting /good FS fight compile by Mindstorm.
I'll keep the strong and fierce fighter and train them to fight with other fierce FS.

Keeping FS is like keeping a betta/fighting fish.
The fighting fish have nice colours and when flare its tail, looks cool.
Same goes for Fighting spider, it got nice long arms, exotic green/blue stripes colour  and when its ready to fight, it will show fierce fighting stance.
Some FS have excellent fighting skill and can fight very well. If you have 2 excellent FS fighting each other, it will be a very exciting fight coz both FS will try their very best to defeat each other and don't ran away easily. 

You can hunt for FS at Spider Lily plants, bamboo leaves, nipah, palm oil, wild pepper, orkid etcs.
Or if u lazy to go catch, you can buy from ppl who have FS like me or Mindstorm.