You would notice little real world difference. The relative speed of a PC to the user is dependent on many variables, and just to rely on processor speed alone, my opinion is you need about a 30-50% processor speed increase (within the same processor family) to make a difference worthwhile.
It also depends on what you're using the laptop for. Other parts are often the bottleneck, for example:
Often the bottleneck when gaming, not the CPU.
Boot times and application loading:
Often the hard drive, so a fast SSD on an older laptop would perform basic tasks better than a slow hard drive with a fast CPU.
If you don't game and want your computer to be simply more responsive you should invest in an SSD. You can easily CLONE the drive. I don't recommend less than 120GB for an SSD (like the OCZ Agility 3) and make sure it's large enough.
A 20% increase in processor speed results in a 20% increase in program execution speed, providing that program is not waiting on other things such as the hard drive or graphics card etc. The speed of the memory or the motherboard will make virtually no difference to the increase of processor speed.
thanks. Its a business software company machine where I have less than a dozen applications open. Toad and MS Office word/large excel docs seem to take a toll. It seemed like it might help but its barely been worth the setup/install effort. More memory surely would help, only 2g now. New machines are on order but in the meantime I can hardly bear to sit and wait for the pc to respond to simple commands.
In this instance, you should opt for more cores, and more memory. None of the apps listed takes a lot of CPU power, but running them all at once will keep a single core or even a dual core at 1.8ghz pretty busy. And with all the power saving features laptops have that slow things down even more, well, I can certainly understand your frustration.
Up until a couple of years ago I was stuck using a 2ghz P4 with 512 meg of memory, and yet they had upgraded our WAN to an exchange server, and wow talk about tossing out the anchor. It took forever to do even simple office tasks, like 5 minutes just to boot and log onto the network!