Difference of certain elements from two lists

Question

I have two lists and I want to take the difference keeping the first elements of the sublists ( X1,X2 below) intact which are the same in both lists. Is there any easier way to do it without explicitly going through each list element and taking the differences except the first one? I tried

listA = {{1}, {X1, a, b}, {X2, c, d}};
listB = {{0}, {X1, a0, b0}, {X2, c0, d0}};
MapThread[{First[#1] , Rest[#1] - Rest[#2]} &, {listA, listB}] 

Output:

{{1, {}}, {X1, {a - a0, b - b0}}, {X2, {c - c0, d - d0}}}

Expected output:

{{1}, {X1, a - a0, b - b0}, {X2, c - c0, d - d0}}

How do I remove these unwanted braces?

Answer 1

Try this:

 MapThread[
 Flatten@{First[#1], 
 If[SameQ[Rest[#], {}], Nothing, Rest[#1] - Rest[#2]]} &, {listA, listB}]

Answer 2

listA = {{1}, {X1, a, b}, {X2, c, d}};
listB = {{0}, {X1, a0, b0}, {X2, c0, d0}};

Expected output:

{{1}, {X1, a - a0, b - b0}, {X2, c - c0, d - d0}}

---

listA - listB // ReplacePart[{i_, 1} :> listA[[i, 1]]]

{{1}, {X1, a - a0, b - b0}, {X2, c - c0, d - d0}}