Sean makes some very good points. I'd also like to add the following from the perspective of an electronics designer:
1. For power delivery, point-to-point wiring can generally carry more current with less voltage drop than a cheaply designed PCB. If a PCB makes use of wide, thick planes for power distribution, it can compete with point-to-point wiring up to the several 10s of amps range. Of course this adds to the cost of the PCB.
2. For low-level signals, a PCB is always preferable. Such signals don't carry much current and benefit from close mounting on a PCB. Surface mount circuits can also be made to be much higher performance than through-hole circuits due to the shorter trace lengths that are possible and, in the case of high-speed signals, the lower pin inductance of the parts. Stripline construction can be used to sandwich the sensitive signals between ground planes which further reduces noise pickup. As Sean said, the quality of the layout is critical. You can have the best circuit design in the world and a poor layout can ruin its performance. A good layout will produce repeatable results for each unit made.
3. PCBs can have much higher reliablility than point-to-point wiring. PTP wiring involves hand soldering, with results dependent on the soldering skills of the assembler. Automated PCB assembly techniques remove that variable from the equation.
4. Repair is generally easier with PCBs.
5. If labor is cheap, PTP can be a cheap construction method, otherwise PCBs are generally cheaper.
PTP wiring has its place, in the wiring of power supplies and the output stages of power amplifiers, but most other applications will be better served by using PCBs.
I have noticed that a lot of audio companies are behind the times when it comes to PCB layout techniques. Most are designed for minimum cost, rather than high performance. 2-layer boards without planes are common. My work involves high-speed digital design as well as high-resolution data acquisition systems and I rarely use less than 8 layers for a design (4 trace/4 plane). Simply incorporating a ground plane improves noise performance markedly.
So, back to your original question - the improved performance of your new amp is most likely due to the circuit design using premium components rather than the use of PTP wiring. Instead of looking for companies that use PTP wiring, I suggest you look for the ones that use multilayer PCB designs (with planes) and high quality passive components such as polypropylene or polystyrene caps and metal film resistors. This will give you a better indication of the skill level of the designer. Rowland and Meridian are good examples.