Both the Walther and the Bersa are good choices.
The Walther PPK is a reliable, well-made gun with a classic history. It was the sidearm of Nazi officers, and was the personal weapon of Adolf Hitler. It’s possible that Hitler personally executed the Stormtroop leader Ernst Roehm with this pistol, and he certainly used it to commit suicide. Of course, the gun went on to greater fame as the sidearm of James Bond.
That said, the gun has a heavy, gritty trigger pull. The Bersa Thunder is a modern derivation of the Walther, with a smoother trigger. It’s also about half the price of the Walther. Unfortunately, there have been reports of feeding problems in the Bersa, so if you are willing to pay extra, I’d suggest the Walther due to its reliability and history.