I was wondering, is it fair to conclude, XOR string encryption is less secure than other encryption method, say Blowfish

This is because for both methods, their input are

1. Unencrypted string
2. A secret key

string XOR(string value,string key)
{
    string retval(value);

    short unsigned int klen=key.length();
    short unsigned int vlen=value.length();
    short unsigned int k=0;
    short unsigned int v=0;

    for(v;v<vlen;v++)
    {
        retval[v]=value[v]^key[k];
        k=(++k<klen?k:0);
    }

    return retval;
}

Is there any proof that XOR encryption method is more easy to be "broken" than Blowfish if the same key is being chosen?