They are hitting you, but just not in the quantity they are at greater distances, how much that difference is is determined by the type of atmospheric interference. For example, thick fog, won't matter if you're 50 or 500 still won't see anything beyond a few feet.
Two different designs with very different purposes in mind. It depends on the Goldilocks zone for each scope, for example, if Goldilocks on the 4.5-28 is between 12-20x for example and Goldilocks on the 1.5-15 is 3-9x. In general most scopes do "better" at lower magnifications so comparing the 4.5-28 and 1.5-15 at 6x may be somewhat of a wash, but as you approach higher magnifications and get outside the Goldilocks zone, that where more of the differences will be seen.
A smaller aperture scope generally has better DOF and may appear more forgiving, I mention during the day because the 24mm objective really becomes a hindrance in lower light.
I would say "weight" more than size, but that could be what you meant. I have not done a comparison of the LHT 4.5-22 and March 4.5-28 directly (even though I have both scopes), hmmmm, maybe another review in the future... but I would say having used both, I would say the March 4.5-28 has a distinct advantage in most areas outside of weight.
It's personal preference, for a crossover style of optic that could be used on a dedicated hunting rig or used on a tactical platform like DMR/SPR, having lower magnification (greater FOV is the goal) is helpful when you need to take a shot at something up close, but you also have to have a reticle that is usable at this lower magnification otherwise the benefits are negated in large part. The narrow FOV of the LHT 4.5-22 really limits it's ability in this capacity which is why I say I would have preferred the LHT had a lower magnification starting point because it means more in a crossover design than having 22x at the top. It is a common fallacy to think that in order to shoot farther one needs more magnification, as many who have experience in ELR shooting can attest, cranking up the magnification at extreme distances can make an image go haywire (see above about atmospherics at distance) as mirage (or what most of us refer to as mirage but is really the effect of the heat waves rising from the surface of the ground), in order to combat this you have to back down on magnification. Last year I shot ELR in 100°+ heat and was using no more than 16x the entire weekend on targets out to 1.5 miles, I had no issue engaging the target accurately at 16x and even 12x (I know because I shot a whole round at 12x and didn't realize it until my stage was done).
The 4.5-28 is a High Master as well and there is some evidence that shows the HM design does help with "cutting through" mirage better than other designs; however, I would say most high end "alpha" grade glass is able to do this. I had my March 4.5-28x52 when I also had my Minox ZP5 5-25 and Tangent Theta 5-25 and I would not say that the March did any better at combating mirage in any situation I had them out in. I will say this, the March 4.5-28x52 HM is definitely a cut above the March 3-24x52 optically (I have no experience with 2.5-25 as it is SFP and they bore me). Do not be deceived by high magnification (unless you're shooting flies and wasps at close range
), for your application you might appreciate a good 3-18 design like the Burris XTR III 3.3-18x50 or even the new Steiner T6Xi 3-18x56. The lower the erector ratio the more forgiving a scope tends to be (all else being equal).
Don't get too caught up in "top glass", there are plenty of "lesser" scopes that do a fantastic job these days, it's not like 10 years ago with the delineation between mid tier and top tier was much greater, there are scopes in the mid tier today that do as good and sometimes better than scopes priced in a higher tier. Try and figure out what magnification at the bottom and what magnification at the top is really going to help and then choose a reticle that best suits your shooting needs. March, Tangent, ZCO and Schmidt all make top quality glass, but not everybody needs this level of glass and certainly don't "need" it in order to get hits on target both near and far.
Sure, just passing on what I've learned and always trying to learn more.