To answer your question about which is better, chuckdawg1999, it depends on a few factors. Currently, there are many more 1/144 Gundam 00 model kits than 1/100 so the 1/144 scale has more variety. However, the 1/100 Gundam 00 kits, especially the Master Grade Exia and GN-X are pretty darn good. The more recently produced model kits, 1/144 or 1/100, are all very nice snap assembly model kits so it just comes down to what designs you like and what is available at this time.
Off the top of my head, I'll mention the 1/144 HG 00 Gundam model kit, which is a very nice kit that is inexpensive and offers a crazy range of articulation.
If you have any favoured mecha designs from Gundam 00, let us know and we'll be able to offer some more information on what to look for or what to avoid.
For a more verbose read on more information about the 1/144, 1/100, and "grades" of Gundam model kits, read on...
There are two main scales for Gundam model kits as you've discovered. 1/144 and 1/100. However, there are also "grades" or basically classes of model kits. Generally, 1/144 kits are either non grade or no grade(NG) or High Grade(HG). There is also First Grade(FG), which is similar to NG. NG and FG are kits you probably want to stay away from because their designs are for quick builds and lack complexity you've likely seen in the 1/144 kits reviewed on Youtube, which were likely HG kits.
As far as 1/100 kits, there are 1/100 NG kits as well as 1/100 HG kits, and the most common being 1/100 Master Grade(MG) kits. From NG to HG to MG, they're listed in ascending order of complexity and price.
HG kits are most often 1/144 scale. The HG kits produced in the last 5 years offer a good level of engineering and design complexity, often showing design elements taken from MG engineering. They are usually in colours accurate to the lineart or animation model but often require extra detailing work via stickers, which are included with the kits. There are also a few spots that may need some paint but they're usually quite minor.
HG kits also come in a variety, depending on the continuity/universe of Gundam the mecha is from. For example, HGUC is for High Grade Universal Century, which is from the base continuity of the Gundam history of fiction. There's also HG SEED, HG 00, HGAW, HGFC, and just plain HG. Don't let the HGxx denominations mess you up, just understand that any HG marked kit is simply HG, regardless of the letters that follow the HG.
Now as far as 1/100 kits, again, you can have NG, HG, and MG kits in this scale range. The 1/100 NG and HG kits have a level of complexity similar to 1/144 HG kits, however, the 1/144 HG kits do seem to have greater complexity than the 1/100 HG kits these days.
So for the most common 1/100 kits, the MG class, these are likely the most bang for your buck with respect to Gundam model kits. They range from $25 to over $100(the upcoming MG "The O" model kit is the most expensive MG yet but it's a special case). The average MG price is around $35 but depending on where you buy it, you can find discounts or you may find the prices are marked up due to import fees.
The most recognized feature of MG kits is likely the "inner frame" concept, which is a mechanical structure, basically a skeleton, that you build first and then build armour components on top of, which results in a more extensive build process. Now the older MG kits don't have extensive inner frames but the more current ones usually have a full inner frame. Inner frames can be great for display, especially if you want to show a Gundam model kit like a mechanical anatomy display piece. However, in some cases, inner frames actually detract from stability of the model kit such as the MG F91 kits as well as some other model kits of Gundam designs that are transformable such as the recently released MG V Gundam.
Another feature of MG kits that many people like is that there are more parts that come coloured in the correct colours so there is far less touch up and detailing work you have to do to get the colours right.
If you haven't found it yet, you may want to check out
http://www.dalong.net, which has an extensive gallery of pictorial reviews of various Gundam model kits as well as model kits from companies other than Bandai.
You may have some questions about the size of Gundam model kits. Seeing as these models use a scale system, the size of model kits varies depending on the fictional dimensions of these mecha(Mobile Suits). The first Gundam, the RX-78-2, in 1/144 scale is about 5" tall. In 1/100 scale, it's about 7.5" tall. I must emphasize "about" because some variations of these models may be off somewhat in terms of height. The NG or HG 1/100 kits, for example, seem to be less accurate in scale than the MG 1/100 kits, which are usually spot on for height accuracy.