OUString concatenation vs OUStringBuffer append

Hi all,
   in a recent patch [1] for String to OUString conversion I replaced the construction of an 
OUString from a sequence of OUStringBuffer.append to a single concatenation of OUString/constant 
strings [2].
Noel Power (whom I thank for the careful review, and is here in copy), correctly asks which way is 
preferred for such an operation: I don't know the answer, can some expert provide me an insight on 
this? I find OUString concatenation easier to read, but this could be not as efficient as the 
original code, or just undesired.

Thanks and kind regards
Matteo

[1]
https://gerrit.libreoffice.org/#/c/4280/

[2]
-    OUStringBuffer aString;
-    aString.append('(');
-    aString.append(static_cast<sal_Int32>(nColMerge));
-    aString.append(',');
-    aString.append(static_cast<sal_Int32>(nRowMerge));
-    aString.append(')');
-    return aString.makeStringAndClear();
+    OUString aRet = "("
+        + OUString::number(static_cast<sal_Int32>(nColMerge))
+        + ","
+        + OUString::number(static_cast<sal_Int32>(nRowMerge))
+        + ")";
+    return aRet;