"My question is simple, which one is faster? And which one is better?"
- Or not so simple: one has to define 'faster' and ' better'.
There is a difference in what is being measured, which depends upon the work that is expected of the system.
If one wants pure raw speed,
with a one-thread task, then clock / instruction-execution speed is the criterion.
If one wants total job throughput and productivity,
with multiple concurrent tasks and threads, then the product of
processors times
clock speed times
degradation factor is the criterion.
Mandrake already has talked about this - clock speed, number of cores, HyperThreading.
Examples: BOINC (see Richard Mitnick's posts) suggests that pure speed is of the essence. In contrast, one who simultaneously is doing heavy encoding AND gaming would suffer severely with only one processor. But also see discussion below of I/O constraints.
(The 'degradation factor' is not quite a constant, but it accounts for the administrative overhead in the computer that is imposed by task dispatching and processor assignment that is required for multiple concurrent tasks. It also accounts for the delays due to the necessity to impose serialization on resources.)
Another consideration must be the I/O utilization. If the system is I/O bound (either from the need for data getting or putting because of the nature of the work, or because the memory working set is too large for the memory available, thus causing paging/swapping) then processor(s) speed is irrelevant beyond a certain point. The system will 'always' be waiting for data transfer. (Race cars and jalopies all wait at a red signal and cross-traffic at the same rate.) This is alleviated by additional devices and channels / buses.
A balanced system is one which has adequate available: processor cycles, memory, and I/O capacity. A balanced system, by definition, is one that runs out of all resources at about the same time. A constantly balanced system is an unattainable ideal, because the real-life work load is never constant.
The real question is: what does one want to do with the computer? Then obtain the resources to support that work. There is no one / best specification that is independent of job imposition. For example, a 'netbook' is adequate for emails and solitaire.
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