To repeat old postings,
Had 'em both.
RS was decent value for the $ and a good size.
Seeker has very slightly better reception, but, you have to pay twice the bucks and put up with it's telephone-pole-like size (Sent it back).
I have heard great reviews on the antennex 800mhz antenna available from scannermaster. It supposedly is better than either of the above mentioned. Check www.scannermaster.com, and click on base antennas, (back of set). It says it has 2.5db gain.
I've been using the seeker for 5 years now (has outlasted 4 scanners) , and it blows away anything else I have tried. The one nice thing about the Seeker is that it works pretty good on the other bands as well, especially VHF.