Hi there~!
My name is Satoshi, i’ve always liked shamisen and wanted to learn to play it.
About a month ago i entered in a japanese music practicing group, however i was told they played shamisen but they actually play sanshin.
I really love sanshin too, but my question is if i can play shamisen musics on the sanshin (one of the teachers borrowed me his sanshin to practise at home).
What is the real difference between sanshin and shamisen?
Sorry for my bad english >_>"
Welcome! 
I’ve only just started with getting a sanshin, but I do play shamisen so hopefully I can help answer this.
You definitely can play shamisen songs on a sanshin, There’s just a couple of major differences to be aware of.
Here’s an example
And here’s one with shamisen and sanshin where they both play the same Tsugaru song so you can see the differences:
So, the big differences are the scale length and the actual playing method. You can’t hit the skin as hard on a sanshin using a tsume bachi as you can on a Tsugaru-shamisen for example, so the striking technique (tataki) is going to be different. The sanshin also has a smaller scale length, so you hear how it he barely reaches the top note of the song (Rokudan), whereas on a shamisen it as difficult since the neck is longer.
But, as long as the tuning is the same, you can play the same songs on both. They’ll just sound a little different, but the notes are the same anyway.
Hey there! I’m mostly going to echo Ian’s points.
Welcome to Bachido, there’s a few other Sanshin players floating around here.
You can play anything on anything! It’s just a question of matching the notes.
Since your scale is shorter on a sanshin, you’ll need to use your ears to get the same sounds. You won’t be able to depend on notation or watching videos unless a sanshin is included! (See below~)
As well, the sanshin doesn’t really have a sawari. It’s got a little twang, but not like the purr of a shamisen.
You’ll also struggle with the percussive end of playing. The sanshin doesn’t have the mass to create the snap or ガンガン we associate with tsugaru or other aggressive playing styles.
To compliment Ian’s link, here’s a side by side comparison of two players doing Rokudan. One on a tsugaru and one on a sanshin.
Hi! I play both sanshin and tsugaru shamisen.
Some people actually do refer to the sanshin as 三味線. It depends where you are in Japan haha.
If you’re interested in tsugaru shamisen music, I don’t recommend the sanshin. You can’t get anywhere near the tone you get with a tsugaru shamisen on a sanshin. The sanshin’s small scale is also very limiting and not suited for the type of virtuosic solo playing you hear with tsugaru shamisen. It’s primary purpose is to accompany singing. But, if that’s what you’re interested in, go for it!
I play both Okinawan sanshin and chuuzao 中棹 shamisen. When I ran out of strings for my shamisen and was waiting for shipment, I practiced Japanese folk songs 民謡 on my sanshin. Sure the tone is different, but for practice purpose I had no problem!