Resin models are just like plastic except they're more expensive, you have to use CA glue, they're heavier, they're more expensive, some of them come with surface pits that have to be filled, they have to be washed very thoroughly before painting and oh, by the way -- did I mention they were more expensive?
The expense part is understandable, given that most resin subjects (particularly in the Real Space category) are limited-run models produced by guys in their garage. Some of these guys are extremely talented and meticulous craftsmen, mind you, but they like to make a profit, so I don't begrudge them that. If you want to build a lot of launch vehicles (and many of them are only available in resin) then get ready to open your wallet.
Then again, you could go the route I've chosen to go and start building card models. You'd be surprised how many launch vehicle models are available online, and while the detail on them ranges from spare to overwhelming, they can be built into fairly decent models and they don't cost you an arm and a leg. Launch vehicles are basically tubes and truncated cones, after all.
You speak of wanting to build the manned launch vehicles used along the way in our moon program. I've done the Mercury-Redstone, Mercury-Atlas, Gemini-Titan and Saturn 1B in 1/96th scale. I posted some photos of them in my album at
http://www.cardmodels.net/phpbb2/album_personal.php?user_id=370, if you're interested.
All of the models except the Gemini-Titan were "free," and by that I'm not including the price of the paper (I generally use a 65-lb. stock) and the use of my color printer. The Gemini-Titan is one of several well-designed card models that come on the "Project Gemini" CD sold by
delta7studios.
All of the models benefit from super-detailing, and once you've mastered a few basic techniques, it's not hard to fabricate pieces. I added plenty of detail to the Redstone, Atlas, Gemini and Saturn 1B, and scratchbuilt items such as the launch escape system towers, etc.
I haven't yet taken or posted photos of my latest four models -- a Mercury-Redstone (in 1/48th scale); a Proton K with a scratchbuilt payload fairing; a scratchbuilt Atlas IIAS; and a scratchbuilt Atlas V Heavy Lift Vehicle. The latter three are in 1/96th scale. Even in that scale, the Atlas V HLV is huge. Erik te Groen (whose models are available at
http://www.lansbergen.net/eng/index.htm has promised us a 1/96th-scale Delta V Heavy sometime this year, and the two rockets will look nice side-by-side.
Speaking of Erik, he is a gifted designer and his models build into wonderful replicas. I've built three of his 1/72nd-scale Delta IIs, (the launch vehicles for MER-A, FUSE and Gravity ProBe B) and a couple of his 1/96th-scale Deltas. He includes a lot of detail.
As for the Mercury-Redstone in 1/48th scale, it can be downloaded at
cardinspace.com. It is a detailed replica and doesn't present too many difficult challenges.
I should note that when building most of my launch vehicles, I've taken to applying the "skins" to appropriately sized model rocket tubes. Aside from adding strength and rigidity, they also make sure everything is straight. If you visit the model rocketry section of a well-stocked hobby shop, you can find no end of tubes in different diameters.