They're sister companies.
Used to collect the raceform results for years, (a couple of years of both Raceform and Weekender), but switched to raceform interactive about a decade ago.
The thought of going back to collecting paper pullouts, and flipping them back and forth (same with the annuals) seems nothing short of hideous.
Do yourselves a favour and get an online subscription to something. I like raceform, but maybe it's just because it's familiar to me. Didn't like the look/feel of computer timeform when I tried that. Some people swear by others at about half the price of raceform, but I feel comfortable knowing I'm using the official formbook.
It's pretty much like having the annuals at your fingertips, with places to interact with it by storing figures, notes, keeping notebooks (nag me type thing), and running queries (system building for want of another expression). The more complex queries can take a while to run, and other software is probably better for that, but for your general day to day stuff and not so complex queries, I've found raceform to come out top. I use some of the RP online (essentially the weekender) for Trainer/Jock course stats/recent form mainly as it's slightly quicker though not quite as indepth , but don't subscribe to it.