Sorry for the delay, I've only just seen this reply! And yes it is a bit confusing with all the similar names :D
R44 is an older regulation, and R129 is a newer regulation (just including for background). R44 seats were supposed to be being phased out this year, although this has been delayed, which means that a lot of manufacturers are phasing out their old R44-compliant models and replacing with newer R129-compliant models.
Both regulations are still legal to use and buy (and will be legal to use for ages) and are both safe. R129 has slightly more strict criteria, so you'll get better protection from an R129 seat in side impacts, and when forward facing.
For rear facing, it doesn't really matter which safety regulation. The safety benefits of rear facing outweigh the slight regulation changes anyway. So if you're only going to use the seat rear facing, then you can just buy whichever one is cheapest
But if you think that you might use it forward facing later on, or you want the increased side impact protection, then the R129 regulation would be worth having.
There are two versions of the Graco Extend, one approved to R44, and one approved to R129, called Extend R129.
Likewise, there are two versions of Joie Steadi - the original (R44) Steadi and the Steadi R129.
While the original R44 Graco Extend was based on the design of the Joie Tilt, which is not often recommended because it has a short shell, the new Extend R129 looks as though it is very similar to the Joie Steadi R129.
Both Graco Enhance and Joie Stages are R44 seats. There aren't newer versions (as far as I am aware).
So, the reason that I would look at Graco Extend R129, or Joie Steadi R129 over the Graco Enhance/Joie Stages is mainly because of that newer R129 approval. But if you're really committed to ERF and you happen to find the Enhance or Stages cheaper, then they would be good options too. In addition, because the R44 regulation doesn't have a height limit like R129 does, the Enhance or Stages might be a better choice if your child is tall and slim.
Hope this isn't just even more confusing
- here's a summary (maybe??)
Joie Tilt+
Graco Extend (r44 version) = Short in shell, avoid, even though cheap (£90ish)
Joie Steadi (r44 version) = Longer shell due to headrest. Usually about £120.
Joie Steadi R129 +
Graco Extend R129 = Good choice due to newer safety reg. Decent size shell, but 105cm limit. Steadi about £160, Graco about £100.
Joie Stages +
Graco Enhance = Older safety standard, but very long shell - good for tall(ish) children. Cost around £130-150. Can be good if you see on special offer.