DV and HDV use the same data-rate, 25 Mbps. so for the same duration, the files occupy the same space. One hour of DV is almost 13 GB, one hour of HDV is also almost 13 GB.
DV results in an .AVI file with 720 x 576 resolution with intra-frame compression, HDV in an .M2T file with 1440 x 1080 resolution with inter-frame compression. Both are compressed, DV by a factor 5, HDV much more and that is why it uses MPEG2 compression.
In PAL country, the framerate of both is 25 fps.
Capturing from tape based machines can only be done over firewire. Ingest over HD-SDI can only be done with cameras that have HD-SDI and require a HD-SDI card in the computer as well (SDI = Serial Digital Interface). Ingest with HD-SDI can be done before any compression given the right camera, but requires a data-rate of up to 1.485 Gbps.
PR capture does not show images and sound during capture of HDV material (haven't tried it lately with the latest versions, so maybe that has been solved now) and that is why some prefer to use HDVSplit. But since capture is nothing more than a digtal transfer of binary data over a firewire cable, there is no quality loss at all and the value of seeing what is captured is rather moot.