Well I've got 75 defence instead of 70, and don't really consider it a "pure", but a "Barrows pure" would be the best way to describe it. Currently my stats are 95/99/75, with 99 ranged, 99 magic, and 95 prayer (still finishing the reqs to do Temple at Sennisten though). So the char is not completely finished, but when it is I will have 99/99/75, 99 ranged, 99 magic, 95 prayer with turm
I find that its fun to PK on as you are still a fairly low combat level for how strong you are, have ALOT of freedom in what style you choose to PK, the loot is good (Expensive hybrid gear, Dharok fights etc.), and you can hybrid very well and are pretty much able to use any gear you'd like. I've had some success with PKing on him so far, but I would easily get owned by people with turm, chaotics, korasi, veng etc. (I didn't have any of these as I am oldschool, quit in 2005 and just came back in June)
But, for the past month I have
only been training, but I'm almost finished! I have veng now, and will have enough QP for barrows gloves by the time I do the 8 pre required quests + Temple at Sennisten. I will also be able to use turmoil then, and will have a rapier to PK with aswell (only a few dung levels away from 200k tokens). So there is probably someone on here who can give you better info about what its like to PK on a barrows pure, as mine is still a work in progress (although I'm SO close to being done and am getting very excited

). If I stop being so lazy though, I could easily have my character finished in about 2-3 weeks. However, I spend way too much time on Sythe now + I have lots of homework, so I am allowing myself more like 4 - 6 weeks until I have met all the requirements for TaS and am fully quested
But the main benefits are simple, and mostly what I stated above.