No, mainly because P4's can scale very high and the chipsets Intel uses offer better memory bandwidth at this time. But the margin between the cpu's is not that big, and Athlons cost less.
P4 Northwood's offer a larger L2 cache and SSE2 instructions. They are also protected by thermal throtlling and will reduce their effective clock speed if they become too hot. Northwoods are built on a .13 micron process.
Athlon XP's have an extra ALU and get better FPU, or if you prefer- more calculating power per Mhz. XP palomino's are built on a .18 micron process, and new thoroughbreds are built on a .13 micron process. The main benefit here is being able to unlock the multiplyer and max out the front side bus.
For temps, I think they're about the same when clocked up to the max.
A dealer speaking of problems is no doubt referring to the product of OEM/retail cooling solutions and case designs, as well as chipset issues such as Via/Nivida infinite loop or creative soundcard drivers or crackling onboard AC97 audio. The fault in these types of problems lies not with the AMD cpu. A custom machine can easily side-step these issues.