router
Just my two cents.
I usually try and mill the widest boards that I can because I like the look in the furniture I make. There is something very appealing about large, single piece construction. That being said I use my 4x8 work table as my "planing station". It consists of two parallel rails running the length with a cross sled with the router fixed in the middle (lots of good ideas on youtube and here). For me, there are three distinct advantages to using this setup versus a large planer/jointer:
1) its scalable. Currently its built on a 4x8 table but there is nothing really stopping me from making it bigger or smaller.
2) cost. For widths say over 13", the cost of planers can be very expensive versus ~$600 for a complete router setup.
3) flatness. a router setup will give you a truly flat piece (whereas a planer really only gives you universal thickness). It can be tricky though in getting side 2 parallel to side 1.
I initially started out with my 1hp router with a 1/2" bit to test it out. Using simple 2x4 construction I was able to get VERY flat pieces (mabye 6" x 24"). I have since scaled up to 4x8 (the biggest pieces I can actually flaten are 33"x7') with a frued 3000 3.25hp (I think its a 3000) with a 1.5" bottoming bit for magnate ($45 I think). I use a 1" overstep with about 1/8" depth of cuts for roughs and then will usually go to a 1/2" overstep with a less than 1/16" depth of cut. Some tricks on certain woods with speeds, feeds, etc, but generally I am very happy with the result. On the largest pieces, while still clamped, the biggest flatness variation I have seen is ~1/32" (I believe that was due to some sawdust build up on the rails that was causing the cross sled to ride high in places).
I have really enjoyed having the big router as its very capable of handling the larger bit during roughing saving quite a bit of time. I think considering how many running hours you can spend doing this, particularly under heavy loads, the bigger HP routers will last a lot longer, though thats an assumption/guess.
Matt