Where's the better place to train?

I would say train on giant spiders in the stronghold of security because they are good xp and they auto attack so you can afk a little bit if you want

I would say it would be lesser demons, their xp and drop rates are pretty good for a level 81.

Dragons because they drop hides and are good for practicing on.

By "best" I'm going to asume your looking for fast easy xp & aren't concerned with the drops.

Combat xp is based on tha amount of damage that you do. Try to calculate what the average damage you can hit with the weapon your wielding. Then find a creature that has HP at about that amount. That way you can usually kill it with one hit before it ever gets the chance to retaliate. You can then stay in that area for a good while killing lots of the chosen creature with little food usage & fast easy XP. Bigger creatures aren't always necessarily better as your more likely to hit 0s.

you could try fist of guthix

if your a member and have done fremmenik isles, then the yaks on jeitznotz isle are unbeleiveable xp. 60k an hour and no food wasted at all. just go with your best weapon, and you probobly wont even need armor. they're level 22 i beleive, and wont hit you very much at all. if you cant get to them, then the experiments in the graveyard near canifis are great, and you just need to start ferkensteins castle to get to them. and lastly rock crabs are always good for 60-70 levels, but thats a last resort situation. hope i helped.

Crandor (Dragon Slayer only)

There are many things down in the Security Stronghold. You should do a magic spell called, Bones to Peaches, which if the monster drops bones you use that magic spell onto the bones and it turns to Peaches, obviously. It heals pretty well, i believe 8 Hp or 10 Hp. Dont take my word on that but I know it heals 8 Hp or more.

If you want to stay up with your prayer try moss giants. If you are just interested in raising your def try the 3rd level of the security stronghold or try lesser demons.

i say experiements or lessers or mabye pest controll
when i got 70 def i used all those strdergies because it gets boring in
one place for a while so switch places around every 1-2 and 1/2 hours.