is there any (naming one is sufficient) other real benefit except RAII and speed of ability to allocate complex object on stack
Yes, and this one is much more important than speed of allocation: speed of access. You can get dramatic performance improvements by getting rid of unnecessary indirections. Herb Sutter gave an interesting talk recently which, among other things, covers his strong love for contiguous memory. An example project he cites got a 50x performance improvement by making life easier for the prefetcher. (Yes, we ware talking about 50 times faster, not 50 percent faster!)