The weight difference is a 99 weighs about 25 lbs without the case. A Featherweight comes in at around 11 lbs. Singer did make an aluminum 99 but they're rare. There are also some Japanese 99 clones out there that are aluminum.
I don't have a Featherweight but I love my 99s. If you fit them with a hand crank they're a favorite with kids.
I haven't noticed any extreme noise with any of my 99s.
The one advantage the Featherweight has other than weight is it is probably better for FMQ due to the vertical bobbin. That advantage might be negated by the very small harp space though.
Rodney

Hi again, everyone!
Still mulling over whether to add a 99 to the herd. Anyone have an opinion on the 99 vs. the Spartan? I know they're essentially the same, but the Spartan doesn't have decals or a light. Anything else that would be noticeable?
Ila

I've seen the Spartan in plastic cases, they are often cracked. Model 99 is much more common here, and I don't think there is any reason to go for a Spartan unless a very nice example happen to turn up. If I'm correct, the Spartan is the later version 99 with back tack lever stripped of all extras that were standard on the 99. A spartan can have been fitted with lights and better case later on, but personally I would prefer a 99 in a domed wooden case, or the suite case type. Here they sometimes turn up on a table, they are nice too.

I also get a little nervous with 99s because their foot pedals can't be replaced as easily. With my Featherweights, I just pull out the plug and put in a different pedal. Some of those old pedals make me nervous.
Ila

Now you are just stalling on minor details. There are 99s with the same plug as the Featherweight, at least those with the larger three prong plug set. I hope someone can confirm on the Featherweight plug variations. All the later 99s I've seen with the backtack have been equipped with foot controller and the standard plugset. A lot of the older 99s has knee lever controller, on those it's not as easy to replace the foot controller because they need a rewirning and the three prong plug set to convert to pedal. There might be 99s somehow wired directly to the motor with out the standard three prong plug, but I have never seen it. The Spartan has a different wiring to a connetion thing under the motor, but I've not seen it on the 99. Knee lever speed control is nothing to be worried about, it works well. If you are very set in your ways you might have to stick to foot controller ;- ) What ever you get it can be fixed, repaired and even altered to your liking. Look out for a machine with the plug set for foot pedal.

the old non reverse 99s are delightful to sew with. tensions are simple to service. Some times they do need to be rewired. The newer 99s do have reverse and they do have a foot control. The Spartan is a good machine. The plastic cases do die. A simple wooden box can be put together to set the machine in. The machines are good, easy to use and service. A brand new motor, foot control and wiring can be bought new and easily attached to any of them. The FW is much more complicated.

Both of my 99's are "hard-wired" to the motor, can't easily change the pedal out. (They're technically both 99K's, maybe that's a difference?) Actually every 99 I've come across personally has been hard-wired. (Just did a tune-up on my MIL's 99K this past weekend; hers is hard-wired too.)

But as miriam said, you can buy a whole new motor/pedal/lamp assembly pretty cheap and they attach VERY easily. One of my 99's came to me for free, mostly because it had really bad wiring and was missing the lamp (it had been simply snipped off, with cut raw wires left sticking out!) - I bought a vintage/used motor/pedal/lamp assembly on eBay for $20 and bolted it on in about 5 minutes. Works great and you'd never know it wasn't the original parts, and absolutely zero knowledge of electrical wiring needed for the job.

You can also order brand new pedal/motor/lamp assemblies online and have them put together for you before shipping, if you prefer new. Probably would cost more than buying used/vintage but certainly an option.

Maybe its' because I'm outside US with 220 Voltage. Motors and speed controllers had to be made differently, and it also opened up the differences in plugs and wiring? Even on machines with knee control lever, the usual setup on the machines is a power cable which can be detached from the machine, with a plug on the side. The foot controllers have the standard three prong plug. It's very nice to be able to exchange information, since there aren't many forums with an interest and knowledge on older machines. I just jump into the conversations and hope to learn something new :- )

This picture is randomly from the web, but the setup is typical of almost all 99s I've seen. The exception might turn up now and then in USA too?

[ATTACH=CONFIG]535902[/ATTACH]

Mickey, I have seen all kinds of wiring configurations. They are not all like yours. Some are hard wired some may all ready have replacement wiring. Some do plug in like yours. Nothing hard and fast about wiring on old machines.

Well, I'll keep my eyes open for a good one around here! I'd rather not ship one -- those little cuties are heavy!
Thanks, all, for the info and advice!
Ila