It's true that any DVD recorder you choose to buy would be much better than your old VCR. But the best DVD recorders go much beyond that. What you should look for:
Format-compatibility
Today, only computer DVD burners are totaly compatible with all DVD formats. The most popular format in DVD recorders world seems to be DVD-R/RW, probably due to support from DVD Forum Alliance members. But a thorough analysis into DVD formats reveals that the controversy upon compatibility differences is rather unrealistic. Plus, beyond the compatibility issue, they all have ups and downs in what other features are concerned: DVD-R/RW can't be played untill they're finalized, unlike DVD+R/RW. DVD-RAM will let you apply some editing functions to the recorded material and access to its content is easier.
You can choose a multi-format unit like the ones Sony makes (DVD±R/RW compatible). Among their top rated are RDRGX7 and RDRGX300. Units like Toshiba DR1 or most models from Panasonic (DMRE60, DMRE100-H, DMR-E55S, DMR-E50K, DMR-E50S, DMR-E30S, DMR-E20, DMR-HS2 and others) write DVD-R/RAM formats.
DVD recorders that burn DVD-RAM discs are nicer because they replicate some TiVo functions, but DVD-RAM discs won't work on any other players except newer models from Panasonic (since 2001).
Hard Drive Incorporated
Panasonic was the first to introduce this feature for DVD recorders, in July 2003; the first model (DMR-E100H) came up with 120 GB hard drive; but newer models from Panasonic (DMR-E500HS) or Sharp (DV-HRD200) have up to 400 GB HD capacity.
Time Slip Function
This feature allows you to simultaneously record and playback and chassing playback. It is similar to what TiVo can do (just like all DVRs), and only DVD recorders that burn in DVD-RAM format can replicate it. So expect to find time slip function on most Panasonic models, the DVR 310-S from Pioneer or Toshiba's D-R2.
Outputs
Progressive scan playback and other upscale outputs are just must-have for DVD recorders. At a rough estimation, more than half of the DVD recorders on the market today feature progressive scan output, and an even greater majority use component video output. FireWire/i.LINK port helps you transfer recorded material from your camcorder, and units that don't feature this output just aren't ready for demanding buyers.
Editing Features
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It is very hard to say which DVD recorder has the best editing features. Though it's a fact that you get more editing functions from DVD+R/RW format vs. DVD-R/RW, and even more with DVD-RAM format and DVD recorders that incorporate a hard drive. It's true it depends very much on what material you want to edit. For example, Sony's RDR-GX7 model is unique for its advanced editing features, including camcorder footage editing, with no need of a computer and additional software. It is also true editing depends on how much you're willing to learn. Editing a DVD-R or DVD+R recording is easier but less versatile.
IR Blaster
With this blaster you can set the unit to record from different channels while you're away; the editors from ConsumerSearch consider this an upward feature for "serious time shifters". You can find it on Toshiba models (RS-TX60, RD-XS32, D-R2), Philips HDRW720, Sony RDR-HX900 etc.
One Touch Recording
Most DVD/VCR combo-owners have learned to appreciate this feature.
Easy User's Interface
This is one of the greatest complaints with DVD recorders; user manuals or remote controls that are way too complicated can make a DVD recorder less eligible. For example, users love a feature that is called OSD. This was borrowed from TiVo boxes, famous as the easiest-use DVRs. Among DVD recorders that feature OSD and also receive very good reviews we can mention: Pioneer DVR-7000, Panasonic's DMR-E60S and DMR-E30S, Philips DVDR80 etc.
High Picture Quality
Depends on a handful of other features like progressive scan output or the ability to upscale VHS tapes quality when transferring them on DVD support. If you want to record your favourite episodes from a TV show for reviewing or sharing with friends, you'll have to record on DVD-R media. It's less expensive, and more compatible with DVD players. Also, use HQ mode for recording, which will give you the best quality picture. Always remember that better quality recordings will require more space on your discs. Usualy, what DVD media or hard drives advertise to be their capacity (in recording hours) is usually in their lower quality mode, SLP. This is said to be sometimes even worse than VHS tape.
Combo Units
Maybe you'd like one of those combination units like VHS/DVD recorder or DVD/VHS recorder TV combos. Or, perhaps, you want to buy one of those DVD/DVR recorders to replace your traditional TiVo box.