"Saving SD into HD format" effectively buys you nothing; the effective resolution is still SD, and you can display SD in "HD format" on any HDTV.
Both Elgato and Hauppage use MPEG4. Not sure which level and profile, but probably the same ones, and very similar to commercial Blu-Ray or DBS. They probably even use the same hardware encoder chip. Elgato uses a proprietary wrapper with a ".eyetv" suffix. The version that they encode for iPad is really quite acceptable. If you use a higher quality than that it can take up to 4 hours to re-encode an hour program to the iPad version, say for a typical i5 computer. I find the Elgato interface a bit more intuitive than the HDPVR, and they have a clever editor that allows editing out commercials pretty easily, with a compacting feature that reclaims the HDD space.
You can, however, encode in full 1080p or 1080i, which is equivalent to the best resolution there is shy of 4K, and is higher than "almost HD" AVCHD, which is a format that is less compatible with what target relatives might have. But to play them direct from a computer, it had better be pretty beefy. If you are going to distribute you should consider just using the iPad quality, which is typically 720p30. The file size is also a bit more manageable. If you send a DropBox invite it is better to post a file at 1.6 GB per hour than 4.1 GB per hour; your relatives will curse you for sending them such huge files and then find them difficult to play without a fast/modern computer.
The HDPVR has a great feature where you can record HD to an SD DVDR blank, and then play that back in full HD on a Blu-Ray, which might be a good way to distribute to friends and relatives who have Blu-Ray. The "SD blank" does not imply SD format; it is still true HD. You basically need a Mac for Elgato, or a PC for HDPVR. I think there are ways to use them cross-format, but in a limited capacity. So if you are torn between the two, just get whatever format is designed for your computer.
Edited by TomCat, 04 July 2014 - 12:41 AM.