Originally posted by samski_1 the Nikon or Canon except that they were big and bulky which is the case with most full frame DSLRs when compared to APS-C options. I believe the K-1 may be slightly smaller than the current full frame offerings by Canon and Nikon but stand to be corrected.
Current full frame DSLRs from lightest to heaviest. Quite a range with the K1 heavier than all but the Canikon flagship models which are nearly double the weight of the lightest options.
However, the weight of the lens and how it balances with the camera is going to have a bigger effect in terms of total weight and ergonomics.
In terms of size, the K-1 is similar to the entry-level FF models and somewhat smaller than the Canikon prosumer and pro models.
Canon 6D II: 685g. 5.7 x 4.4 x 2.9" (13" total)
Nikon Df: 708g. 5.6 x 4.3 x 2.6" (12.5")
Nikon D750: 750g. 5.5 x 4.4 x 3.1" (13")
Nikon D610: 757g. 5.6 x 4.4 x 3.2" (13.2")
Canon 6D: 770g. 5.7 x 4.4 x 2.8" (12.9")
Canon 5D IV: 800g. 5.9 x 4.6 x 3.0" (13.5")
Sony a99 II: 849g. 5.6 x 4.1 x 3.0" (12.7")
Canon 5D III: 857g. 6.0 x 4.6 x 3.0" (13.6")
Nikon D810: 880g. 5.7 x 4.8 x 3.2" (13.7")
Nikon D850: 915g 5.7 x 4.9 x 3.1" (13,7")
Pentax K-1: 924g. 5.4 x 4.3 x 3.4" (13.1")
Nikon D5: 1415g. 6.3 x 6.2 x 3.6" (16.1")
Canon 1DX II: 1530g 6.2 x 6.6 x 3.3" (16.1")
Comparing the 24-70mm f/2.8 from lightest to heaviest:
Pentax-D FA 24-70mm f/2.8ED SDM: 787g. ($1100 usd)
Canon EF 24-70mm f/2.8L II USM: 805g. ($1750 usd)
Nikon AF-S NIKKOR 24-70mm f/2.8G ED: 900g. ($1800 usd)
Sony Vario-Sonnar T* 24-70mm f/2.8 ZA SSM II: 974g. ($2100 usd)
Sigma 24-70mm f/2.8 DG OS HSM Art: 1020g. ($1300 usd)
In general, Pentax wins in price at many levels. Many bemoan of the lack of third party lenses, but in most cases those lenses are heavier, not WR, and often not AF. Ultimately, everyone has their own priorities: price, features, quality, ergonomics, or someone elseʻs recommendation or perceived approval.