1) which one of mentioned miners is more durable and reliable technically with less break down probability ? (I heard that s9 after few months face some problems like drop in the hashrate )
I don't have much experienced on Avalon but in s9s it is still a good choice because my miner still alive and running. I think it depends on our hand how do we care our miner because I'm doing maintenance every 2 weeks removing all dust is very important because if your miner is full of dust the miner temp will become higher that might destroy any parts from your hashboards.
2) If you have used any of them please share your own experience ?
Just like what I said above I don't have experience on using Avalon miner but I'm sure other miners will recommend s9j because you can overclock it through SSH and reach 19th/s.
3) generally which one do u suggest and why ?
I already answered it above.