I registered just to answer your question. I have been using Smartlink 3 months now. My friend said that the pings were good, and the speed was good, so I took it.
The pings are only good to Indian and Singaporean servers. So if you're playing games like CSGO or particularly games which have servers in India or Singapore, you can expect to get a ping of around 60 for singapore servers and 5-10 for indian servers. But if you're like me, who plays a variety of games like battlefield 4, DayZ, or games which don't have Indian servers or have a low number of Singapore servers, you're out of luck. The ping on servers in Europe is around 400ms to 500ms. I did a tracert and found that it takes a pretty stupid path for the data to get here. I used to get a ping of 140 on MTNL, it is 400 on Smartlink. As the ping is high on European servers, the speed also decreases. I don't get more than 2 Mbps on my 6Mbps plan if the server is located anywhere in Europe. As for the speed normally, prepare to get inconsistent speed. Generally speaking, most of the servers are located outside India, that means, you'll get low speeds on those servers. Don't expect to get 6Mbps on Dailymotion or other sites. Additionally, the connection is REALLY unstable. Most of the time, facebook videos stop buffering in the middle; I get 6Mbps for a minute and after that, it is down to 0. There are also frequent disconnections and I have to call them up every 4 days. On the other hand, the torrents are cached. If you use a lot of torrents, you'll get 32Mbps on them. Uplay is also cached and I get 32Mbps on it. Steam and Origin are cached randomly. One day I get 32Mbps on them, the other day it's 6Mbps. Oh yeah, and if you want to use port forwarding, Smartlink doesn't allow that.
In short: they have an unstable connection. You can't play games like Battlefield on it and there will be frequent disconnections.
Give me a list of ISPs in your area, and maybe I can suggest you on what to take. As for now, if you get good ping on your current ISP, I'd say, stick to it.