I have .30 Herrett, .22 LR, .357 mag, and .44 mag. First off, I would definitely keep the .35 you have becasue if you're anything like me, you will regret it if you give it up. The .357 I love, but since it fires the same bullet that your .35 does, and yours is more capable with heavier ones while also being able to be loaded down to as light as you want, the only advantage I can think of there is the plentiful and often free brass. The .44 mag isn't bad with either my Unique or 2400 loads, but there have been times it bit me a bit before I got used to it and learned to control it. The .30 herrett is also a great shooter, but requires you to form your own brass, which is something many people aren't willing to do. I think it is worthwhile though, and although I havent had a chance to try it on game yet, the accuracy on paper is great. In the end, if the .35 is the only thing you have currently, and I say this in all seriousness and not trying to be a smart alec, but I would say get a .22 LR. It is cheap and easy to shoot, and it will allow you a lot of cheap, yet very beneficial practice, and is equally great for both paper and small game, so I see it as a very versatile caliber, having taken squirrel, rabbit, coyote, hog, and several other species, with some of them getting into the 350-400LB range. Not saying some of those were the smartest decisions I have ever made, but I had to find out the limits for myself and did so.