Which of sprintf/snprintf is more secure?

The two expressions you gave are not equivalent: sprintf takes no argument specifying the maximum number of bytes to write; it simply takes a destination buffer, a format string, and a bunch of arguments. Therefore, it may write more bytes than your buffer has space for, and in so doing write arbitrary code. The %.*s is not a satisfactory solution because:

1. When the format specifier refers to length, it's referring to the equivalent of strlen; this is a measure of the number of characters in the string, not its length in memory (i.e. it doesn't count the null terminator).
2. Any change in the format string (adding a newline, for example) will change the behavior of the sprintf version with respect to buffer overflows. With snprintf, a fixed, clear maximum is set regardless of changes in the format string or input types.

For the simple example in the question, there might not be much difference in the security between the two calls. However, in the general case snprintf() is probably more secure. Once you have a more complex format string with multiple conversion specifications it can be difficult (or near impossible) to ensure that you have the buffer length accounted for accurately across the different conversions - especially since a previous conversions don't necessarily produce a fixed number of output characters.

So, I'd stick with snprintf().

Another small advantage to snprintf() (though not security related) is that it'll tell you how big of a buffer you need.

A final note - you should specify the actual buffer size in the snprintf() call - it'll handle accounting for the null terminator for you:

snprintf(buff, sizeof(buff), "%s", name);

I would say snprintf() is much more better until I read this passage:

https://buildsecurityin.us-cert.gov/bsi/articles/knowledge/coding/838-BSI.html

Short summary is: snprintf() not portable its behaviour change from system to system. The most serious problem with snprintf() can occur when snprintf() is implemented simply by calling sprintf().You may think it protects you from buffer overflow and let your guard down, but it may not.

So now I am still saying snprintf() safer but also being cautious when I use it.