DA 55 - 300 v DA* 50-135
It's developed a bad rep in the past because of SDM failure, but fwiw I've had no issues with mine, which could be luck, or the fact that I give it a 'run' every two weeks whether I've shot with it or not. The number of failed SDM reports has dropped down to just 'noise' levels, which either means later models have an improved SDM, or no-ones buying them!
Sometimes its a bit slow to wake up first time I use it, AF wise its no speed demon, and its heavier than the 55-300, but overall, great lens!
I agree with JohnX's comments. I have both of these. The 55-300 proved useful (and of course it has a longer reach) but I found focusing sometimes problematic at longer lengths, where the smaller aperture also made it harder to push up the shutter speed as needed. The 55-135 feels and performs so much better over its range, with a bright and constant aperture. So it's the one I carry around with me and use a lot - the image quality means it will take cropping if it won't always reach as far as I need. The 55-300 now mostly stays in its case.
Footnote: I have to confess that have bought my first DA* lens, I've since fallen for a second-hand DA* 200mm too - another lovely piece of work!

A few pictures on Flickr
If you really want a da* lens you should get a
Da* 60-250mm if you have a kidney to spare
cheers Neil
pentax k3
DA* 300 f4 DA* 50-135 f 2.8 smc DA* 16-50 f2.8 50mm f1.7 pentax1.4xhd converter

Panasonic Dmc Fz200
My 50-135 has a failed SDM motor but I still haven't got around to getting it fixed. It is so good a lens that manual focus is a small price to pay for the quality of image it makes possible. It is large and heavy though, f2.8 usually is.
The 55-300 on the other hand, is compact, for the range it gives you. For the price it gives very good value.
The best choice is buy both or carefully decide. They are two different lenses in the end, one high quality, heavy but more limited range. The other lighter, long range but of a lower quality. You pays your money and takes your choice.
Bob
Hi
If you really want a da* lens you should get a
Da* 60-250mm if you have a kidney to spare
Too much of a beast in size and weight!
flickr ID: SteveW46243 or sw46246
DA AL 35mm f2.4, K3,18-135 WR, DA 55-300, Pentax KX, K5 x 2, 18-50 50-200 kit lenses, Tamron 17-50 f2.8, Fuji X10, 2x Mamiya 1000s 2x 80mm f2.8, 150mm f3.5, 210mm f4, Yashica 124G TLR, 2x Yashica FX3 Super 2000, Tamron 28mm f2.8, 90mm SP f2.5, 135mm f2.5, Olympus 35RC, 2x Yashica FX2, Kodak Pocket Instamatic, Kodak Box Brownie
flickr ID: SteveW46243 or sw46246
DA AL 35mm f2.4, K3,18-135 WR, DA 55-300, Pentax KX, K5 x 2, 18-50 50-200 kit lenses, Tamron 17-50 f2.8, Fuji X10, 2x Mamiya 1000s 2x 80mm f2.8, 150mm f3.5, 210mm f4, Yashica 124G TLR, 2x Yashica FX3 Super 2000, Tamron 28mm f2.8, 90mm SP f2.5, 135mm f2.5, Olympus 35RC, 2x Yashica FX2, Kodak Pocket Instamatic, Kodak Box Brownie
I quite agree I use mine mainly portraits
cheers Neil
pentax k3
DA* 300 f4 DA* 50-135 f 2.8 smc DA* 16-50 f2.8 50mm f1.7 pentax1.4xhd converter

Panasonic Dmc Fz200
(Don't tend to use burst fire mode on these subjects much anyway)
Bob
sportyman531
Member
Ramsbottom, Bury, Lancashire
flickr ID: SteveW46243 or sw46246
DA AL 35mm f2.4, K3,18-135 WR, DA 55-300, Pentax KX, K5 x 2, 18-50 50-200 kit lenses, Tamron 17-50 f2.8, Fuji X10, 2x Mamiya 1000s 2x 80mm f2.8, 150mm f3.5, 210mm f4, Yashica 124G TLR, 2x Yashica FX3 Super 2000, Tamron 28mm f2.8, 90mm SP f2.5, 135mm f2.5, Olympus 35RC, 2x Yashica FX2, Kodak Pocket Instamatic, Kodak Box Brownie