Yagi or BiQuad for use with WRT54G

I am planning to use the WRT54G in client mode with Tomato firmware to access an access point from a friend who lives in another unit across the street. I don't have line of sight but I can see a weak signal without the antenna. I am hoping the signal will be stronger and the connection will be stable with the antenna. The router and the antenna will be placed next to the window and close together.

I have looked around and see a wide variety of antennas being sold on ebay, including Yagi and BiQuads.

Yagi Antennas:
2.4G - 3G 11db gain external yagi antenna Wi-Fi - eBay (item 370125222797 end time Dec-11-08 11:00:09 PST)
or
YAGI High dBi Antenna 802.11 Wireless Wifi 2.4ghz NEW - eBay (item 400015612641 end time Dec-13-08 19:59:10 PST)

I am assuming I will need a RP-TNC to N Cable like this one to connect the antenna to the WRT54G?
72" RP-TNC to N Cable BiQuad Cantenna Yagi Pigtail - eBay (item 220308942601 end time Jan-07-09 16:05:03 PST)

Just needed to know what are peoples general experience with the BiQuads vs Yagi ...which ones are better for which setup.

Thanks

Theoretically, one antenna of X gain should be functionally identical to another antenna of X gain. The gain comes from concentrating the RF into a small area. X dB of gain = Y degrees of sky.

The difference is geometry and mounting. A yagi occupies a long cylindrical space, needs to be mounted by the end. A patch or biquad occupies a flat square area, can he hung in a window and the curtains pulled over it.