@Flabadyflue that is the dumbest analogy in the world. The fact that it's a hobby is exactly why sniping is such a stupid concept. There is absolutely nothing at stake here.
@vkj3 all you are doing talking from pride. And you aren't getting the point. First, it's not a wasted effort if you continue. It's only wasted if you believe no one else will read your work now. And if you believe everyone prefers the other work compared to your's then honestly you should be happy that someone capable of giving everyone what they want stepped up, unless you're letting your pride get in the way. Secondly "They picked up from where we left off." I don't see you redrawing the entire manga by hand to convey it to the English audience. And a less extreme one, are you going to japan and buying the mangas and cutting out the pages and scanning them yourself? The very foundation of scanlating relies on a community effort. Saying that someone should have to start over from chapter 1 and work their way up in order to not be 'sniping' is just dumb and once again pride talking.
Now as for their criticism of your pace, in all honesty what they said is true. Realistically it's kinda foolish to believe that your pace can speed up. Maybe it can, there are no certainties in this world. But you are 'set' at a weekly schedule as is. It's not a "Usually it's weekly but occasionally we get it faster." If you had more staff, you have more links in the chain, more times the project has to be sent to someone and then wait on them. And they're shooting for a chapter essentially between every 1 to 2 days. That is a daunting and nearly impossible task for a larger team to do unless they have little to do do IRL, and it's unrealistic to expect that. So them making the assumption that they can't get a chapter out every 2 days if they join you is a realistic assessment of the situation. They didn't say you can't go faster, they said you can't go as fast as they plan to.
Saying "Sniping is sniping" is a dumb justification, because I'm not saying the didn't do what they did. I'm saying you shouldn't treat what they're doing as some shameful or dishonorable act. It'd be different if you were caught up or had plans to catch up, and they were releasing the same product as you. But that's not the case. They are releasing something different from what you plan to do. Just like in the anime subbing community, there is a place for speed products and a place for high quality products. Some people want one, some people want the other.
If you're bothered by the fact that someone thinks that working with you wont get the result they want so they work separately from you, maybe you should rethink why it is you're doing this in the first place.