Desktops are always better that laptops no matter what ever your processer is, it going to run slower on a laptop. A pentium 4 1.8 Ghz is faster than a Celeron 2.5 just because it is porley made and i smade to run with less power. Running one program it is ok but more than one program or a high priority program (aka mbcaster) it will be slower. Also a laptop has to run more processes than a desktop. The fbs (frond-side bus speed) of a laptop is slower than on a desktop as well as the RAM. Laptop DDR2 (fastest RAM out for PC) runs at 400Mhz. while DDR2 for desktops runs at 533Mhz.
As for the wireless, my wireless MIMO runs at 1Gig a second and it runs just fine.(Faster and better than 100mb wired).
My laptop is faster than my Desktop(processing wise) both runing 400mhz FSB, my laptop is a dualcore turion and desktop is a single core Athlon 64 runing dual chanel memmory and OC'd to 2.5ghz(about 4000+speeds) .. the turion is just a simple dual 1.67ghz.
My laptop hosts very well especialy when setting the priority on MBCaster to higher than normal, doing this on my desktop just kills it.
btw, "good" desktops are runing 1.3ghs FSB and the most common FSB's are 667 and 800, not that its all that important with the right timings and settings theres allways a middle ground to be found. theres also DDR3 which jumps up to about 1.8ghz for FSB ovbiously price vs performance vs size its not even worth it.