I think it is worth the extra cost. I am sure you are hoping to get 5-10 years out of this set and to look at the price difference over the long hull that does not add up to much per year for the superior technology.
No question the 55 is a better set

keep in mind the extra 3" makes the 55" 12% bigger, so just the size difference should easilly add 12% in extra costs. (see below)
55 inch 16:9 Set 52 inch 16:9 Set
4:3 (1.33:1) NTSC mode [12.1% larger] 4:3 (1.33:1) NTSC mode
Your viewing area is 36.0 in(w) x 27.0 in(h)
Total viewing area is 972 sq in.
This is the equivalent of a 44.9 inch 4:3 TV
Your viewing area is 34.0 in(w) x 25.5 in(h)
Total viewing area is 867 sq in.
This is the equivalent of a 42.5 inch 4:3 TV
16:9 (1.78:1) native mode [12.0% larger] 16:9 (1.78:1) native mode
Your viewing area is 47.9 in(w) x 27.0 in(h)
Total viewing area is 1293.3 sq in.
This utilizes the full display of the 16:9 TV
Your viewing area is 45.3 in(w) x 25.5 in(h)
Total viewing area is 1155.15 sq in.
This utilizes the full display of the 16:9 TV
16:9 (1.85:1) letterbox mode [11.8% larger] 16:9 (1.85:1) letterbox mode
Your viewing area is 47.9 in(w) x 25.9 in(h)
The diagonal size is 54.5 in
Total viewing area is 1240.61 sq in.
Total area is 52.7 sq in. (4.1%) smaller than 1.78:1
Your viewing area is 45.3 in(w) x 24.5 in(h)
The diagonal size is 51.5 in
Total viewing area is 1109.85 sq in.
Total area is 45.3 sq in. (3.9%) smaller than 1.78:1
16:9 (2.35:1) letterbox mode [11.8% larger] 16:9 (2.35:1) letterbox mode
Your viewing area is 47.9 in(w) x 20.4 in(h)
The diagonal size is 52.1 in
Total viewing area is 977.16 sq in.
Total area is 316.1 sq in. (24.4%) smaller than 1.78:1
Your viewing area is 45.3 in(w) x 19.3 in(h)
The diagonal size is 49.2 in
Total viewing area is 874.29 sq in.
Total area is 280.9 sq in. (24.3%) smaller than 1.78:1