There are no comparison charts for the two HDTVs. You'll need to read up on the two HDTVs to determine which one offers the features that best suits you.
The one big difference between the HDTVs is that fact that the Samsung 6/7 series has LED edge backlighting which allows the Samsungs to consume a little less electricity than the LG. However, LED edge backlighting has the disadvantage of not being uniform across the entire screen, which is the main complaint about edge backlighting from several user reviews.
The LG LH70 uses traditional CCFL backlighting.
The LG LH90 uses LED backlighting with local dimming capabilities. However, it is not a slimline HDTV. I have the 47" LG 47HL90 and I have to say it is pretty nice overall. It's advertised as a "240Hz" HDTV, but it really is only 120Hz with backlight strobing effects.
Post your question over at AVSforum.com, perhaps someone there can answer your question.