Here's a good guide by kmjt http://www.sythe.org/showthread.php?t=1265575. It has things about VPS's and different companies. If you are using Simba, you need around ~500MB RAM/bot.
Any negative feedback must be unrelated to runescape botting. Between my friend and I we had 16 8gb servers and never had a problem with it. Of course the server will lag if you put too many bots on it which is why you have to do some testing to find the optimal amount of bots to run. You want to push your server's limits because obviously the more bots you can run the more profit, but on the other hand you want to make sure you don't overdo it which could lead to lagging and all of your bots turning off while you are sleeping at night. Any downtime is extremely bad,
Serverloft does have sister sites which sell servers a lot cheaper and are the same (I think), but personally I never found/used a server from a sister site. I stuck with what was working for me. Sister sites may sell cheaper but often they have hidden fees such as a fee every time you want to restart your server. As a botter you will most likely have to restart your server a lot so I liked the fact that serverloft offered free reboots for example.
Don't jump in head first. Start small and make sure you are profiting monthly per server than expand from there. You don't want to get overwhelmed, even 70 is a fairly large amount of bots to run.