whats the difference between these low lead cars and the track car blocks and which would one be better for the genoa sheets. i currently have the track car style which need to be replaced. i have a catalina 30.
Traditional track car blocks, (the taller ones) can lead to problems with the lead angle to your winch if the coaming or winch is not sufficiently higher than the deck track. Too flat a lead angle (should be at least 5 degrees below horizontal) can lead to overrides during tacking. The lower profile blocks can help but are often pricier.
Another reason for the lower wider blocks was a racer's trick to be able to run two sets of sheets for quicker sail changes - not a cruiser's requirement as a rule - but the wider sheave avoids some of the hangups that can occur due to a kinked sheet that can jam in the narrower blocks.
The stand up blocks in the first photo would probably be okay. They worry me a bit when they get real heavily loaded, but on a boat your size it's not a huge issue.
My preference would be for the genoa lead blocks in the second photo, for the good reasons Faster mentioned.
We have both the genoa lead blocks on our track, as well as the stand-up blocks. The stand up blocks are at the aft end and are used for the spin sheets (our track is outboard on the cap rail and is VERY long).
One point, the low lead cars only pivot, unlike the taller genoa cars, which can pivot, tilt and twist....so, if the angles from the genny to the genoa cars isn't great, the taller cars would work better.