Surfing Waves

Last year, spent 4 months in Bali surfing airport reefs and kuta beach, not as crowded as the bukit.

This year, I want to go somewhere different, planning to stay for 5-6 months starting in May.

I don't like to travel around alot, so I just want to goto one area, close to a city that has an immigration where I can do my monthly visa extensions.

Budget $4000US/month, although would prefer to spend a little less. Surf level is solid intermediate, with decent reef experience.

My thoughts were either Nias or Mentawai, but I don't have experience in either.

Let’s run the difference of all three places past you, as there is quite a lot to consider.
The Mentawais and Nias are , firstly island group (Mentawais) or Island Nias, they are roughly 150 kilometers off the Northvwestern Sumatran Coast so you need ferry or resort boat transfer to get there.
Resorts range at around US $ 2000 for about 10 days and are heavily booked for the season.
Nias as a single island has several places providing accommodation there are a number of breaks on the island.
The prime break you need to have a good A game to be able to claim a place in the pecking order and handle the barrel, right handed.
A ride of your life type wave!

Mentawais , range from full resorts to feral home stays. Similar price range for resorts with a number of advantages, pick up from Sumatran port by resort boat and resort transport to breaks at your personal,skill level, ( from pro to fat once a year business man level) often internet capable
Usual included in your tariff.
Down the scale you may find the ferry costs and boat trips to breaks an add on.
Most of the breaks are on other island so boat transport essential.
Go further down , feral home stay, you might have a wave in front of where you are staying, a dodgy cano and outboard + guide that you need to pay for all and some journeys to breaks denied!

You will need to have really good travel insurance ( most resorts require it and need to see documentation) medivac from anywhere in Indo, will cripple you or your family severely.

Krui is on the mainland on the southern end of Sumatra you can fly there!
A number of breaks accessible by transport , again a full,range of accommodation from 3 star to pretty basic, lower down the scale you will need to be near a break and/or have a working relationship,with a driver or your own motorbike.
There are minor turf wars over some breaks by resorts and parts of some beaches are used as toilets so watch your step!

It looks like you have the visa thing wired but tripping from the Mentawais or Nias will require, going 150 Köms back to,a city on Sumatra.
Krui might have immigration facilities, or you could apply for a longer visa first off.

Krui is beach and reef breaks, Mentawais and Nias full on reef breaks .

Budget on your scale and need probably Krui.

BTW what happened to the Fiji trip plan? The

Yeah, I just replied to your other post, I was thinking Coral coast before, but heard Mananucas was where to be, I guess its due to the tradewind favorable to west facing breaks? (same situation in Moorea, Tahiti where I am now).

The only option would be funky fish, which is fine for me. Going to Fiji is one less flight each way, so I'm guessing may as well do Fiji due to lesser crowds?

I think you need to rethink funky fish as it is two sets of barrier reef island arcs behind the cloudbreak and other breaks Reef!
Sure it is only a 10 minute boat ride away, but most of the break you access are well beyond beginner intermediate level skills!