Q: Which is better: Apple PowerBook G4, or Apple iBook G4?

Initial thought, don't get either. The computing world has left the G4 platform behind. Maybe if all you want to do is email you'd be OK, however, much else with internet access may be frustrating.

There's not a lot of difference. Here's the specs on both.

http://www.everymac.com/systems/apple/powerbook_g4/index-powerbook-g4.html

http://www.everymac.com/systems/apple/ibook/index-ibook.html

Make sure you get one with at least a 867MHz processor since they will run Leopard OS 10.5. OS 10.5 is the max OS for PowerBooks and iBooks.

Make sure you get the system discs with the laptop, because they sell for over $100, if you can find them.

Both the PowerBook and iBook are semi- obsolete. You might want to get a MacBook since it has an Intel processor and can run OSs higher than OS 10.5.

 Cheers, Tom

They are both officially obsolete.

Obsolete products are those that were discontinued more than seven years ago. Apple has discontinued all hardware service for obsolete products with no exceptions. Service providers cannot order parts for obsolete products. These include ALL G4 models. On November 23, 2011 all G5 models were declared as 'vintage'. Obsolescence cannot be far behind.

http://support.apple.com/kb/HT1752?viewlocale=en_US

I don't play SWTOP, however, it looks like it's a Windows-only game if you want to load it and run it on a computer. Otherwise, you're playing it online over the Internet.  Besides a good, fast Internet connection, you'll want a mac with good video horsepower. Generally, mac notebooks with a video processor with it's own memory are better for gaming than those with a video processor that shares the system memory.

As Tom said, at least get a system with an Intel processor, like the MacBook or MacBook Pro, in notebooks. Earlier systems, from around 2006+ will be less expensive, however, don't know about used pricing.   

Allow me to suggest that you first research the games you wish to play and become thoroughly familiar with their system requirements, especially the requirements for video hardware. Then look at computer models with that in mind. If you don't understand the hardware jargon, find a friend locally who does and ask for help.

We see plenty of reports here from people buying the cheapest Mac notebook to save money, knowing full-well it has entry-level graphics hardware, and then get mad at Apple when some high-end game won't run because it needs more powerful gfx hardware. Don't join that club, please.

The Dell you linked will not meet the sysreqs for SWTOR as shipped. As it has the lower-performing Intel GMA integrated graphics, you'd have to increase RAM to 2GB and then it still may have to run at the lowest resolution settings. I suspect it will disappoint you.

Observations:

---New games need newer computer models and that cost more.

---Few notebook computers--regardless of make--are good gaming computers. Heat is the enemy of any notebook and most high-end games run all the hardware at near-capacity, and the laptop get really hot.

Research, please, so you aren't disappointed.

Allan Jones is right, get a new laptop with a dedicated video card, I recommend Lenovo and Apple (obviously).

Define your price limit please.

I do not know what used PCs are going for but I am sure someone has a source to guide you. As for used Macs a site called LowEndMac regularly scans the used Mac market to compare prices. This link is for the MacBook which is the only intel Mac laptop that will come close to your budget.

A quick look shows a lowest price of 1.83 GHz Core Duo, 1/80/Combo, $279.99  which would not be a good Game machine.

http://lowendmac.com/deals/best-macbook-prices.html

Forget the PowerBook and iBook, get a MacBook Pro for gaming and designing (or Mac Pro). Or the MacBook Air for internet surfing and non high graphic applications

If you want to earn more money, get a HP dv7, I have one and I play Kerbal Space Program, Sarcraft 2(Wings of Liberty and Heart of Swarm), and Portal 2. It holds up really well. I forgot to menchin that I got it free from my cosins, one of them spilled there drink on it. But it works REALLY well!